Due to my research areas, I will not be able to fully answer your question, mainly, analyzing and comparing patterns that relate to all the failed invasions of India. However, I do have the resources and answers to explain part of your question, concerning Alexander the Great. Let’s begin.

One of the greatest misconceptions about Alexander the Great is after his victory at the Hydaspes River, he immediately retreated back to Persepolis, his Persian capital. Instead, Alexander the Great did extensive campaigning down the Indus River (now parts of modern Pakistan and Kashmir) for nearly two years after this “final” battle.^1 One of the hallmarks of this campaign was the Macedonian army’s brutality against the natives. Due to the prospect of being surround by the hostile Mallian peoples in the lower Punjab region, Alexander’s army conducted “a conquest of terror”^2 and “in a mere week, they [Macedonians] had subdued the Mallian towns west of the Hydraortes, massacring all in their wake as had become their custom.”^3 Alexander’s army then encountered the Brahmans, an Indian intellectual elite who traced their roots to the late Vedic period or approximately 500 B.C.^4 Alexander committed a huge blunder when encountering these people as Worthington states,

During the Malli campaign, Alexander had attacked a city populated by the Brahman’s and slaughtered them indiscriminately. His actions demonstrated his misunderstanding of the role that Brahman’s played in Indians society and the respect in which they were held. His blunder came back to haunt him when the Brahmans orchestrated a massive revolt as he prepared to leave India.^5

This revolt saw the alliance of the subjugated Oreitae people and the Brahmans who were only defeated after Alexander’s satrap, Leonnatus, killed 6,000 of them in open battle. This revolt (along with his disastrous march through the Gedrosian desert) became an ignominious end to his campaign in all of Central Asia.^6 As one can see, Alexander campaigned extensively along the periphery of the Indian nation, encountered societal elites, and destroyed several cities on the outskirts of India, but failed to conquer the area due to several military blunders, including his massacre of the Brahmans.

The Macedonian army’s unwillingness to travel further explains a second reason for Alexander’s incapability of penetrating further into India. After his victory against Porus at the Hydaspes, the Hellenic army’s next hurdle, the Nanda dynasty, was gargantuan in nature due to the size and population of the region (their capital at Pataliputra reputed to have over 400,000 people alone). Despite Alexander’s pleas to cross the river and march east, his men negatively responded, refusing to go further. The mutiny’s head spokesmen ,Coenus, remarked that,

their energy was running out, their bodies were weakened from wounds, their clothes were in tatters, their armor was falling apart from age and damage, and they needed to return to their homes and families.^7

Alexander only convinced his men to campaign more (though not east) only after a brilliant three day display of speeches, bribery, and seclusion to his quarters.^8 It should be noted that this was not the army’s first mutiny. An earlier rebellion (maybe only rumored) took place after disdain for Alexander’s growing orientalism (like his incorporation of proskynesis in court decorum), lead to the death of Alexander’s greatest critic, Parmenion.^9
It should also be observed that disdain for their warrior king was also rooted in the inclusion of native recruits into the army. 30,000 of these new warriors, called epignonoi, were incorporated into the army after his Indian campaigns in 324 B.C.^10 Thus, the army’s resistance to marching further ended Alexander’s hopes and ambitions to conquer India.

In conclusion, Alexander’s failure to invade India was multi-faceted and complex. It included Alexander’s military blunders on the outskirts of the nation, leading to native’s rebelling and insuring further discontent in the future. Another reason for his lack of success was his army’s unwillingness to go further east. Ultimately, Alexander’s pre-mature death may also have contributed to his inability in defeating the nations of India. Still, Alexander saw some success in the east, challenging some misconceptions that he did in fact conquer parts of "India", but let’s not get too ahead of ourselves.

Footnotes

1. Dupuy, Ernest, and Dupuy, Trevor, The Encyclopedia of Military History from 3500 B.C. to the Present (New York: Harper & Row Publishers, 1970), 53.

2. Ian Worthington, By the Spear: Alexander the Great , and the Rise and Fall of the Macedonian Empire (New York: Oxford University Press, 2014), 255.

3. Worthington, By the Spear , 255.

4. Worthington, By the Spear, 257.

5. Worthington, By the Spear, 280.

6. Worthington, By the Spear, 260.

7. Worthington, By the Spear, 252.

8. John Keegan,The Mask of Command, (New York: Viking Penguin Inc., 1987), 59.

9. Worthington, By the Spear, 216-220.

10. Worthington, By the Spear, 214.

Sources

1. Dupuy, Ernest, and Dupuy, Trevor. The Encyclopedia of Military History from 3500 B.C. to the Present. New York: Harper & Row Publishers, 1970.

2. Grant, R.G. Commanders: History's Greatest Military Leaders. New York: DK Publishing, 2010.

3. Keegan John. The Mask of Command. New York: Viking Penguin Inc., 1987.

4. Worthington, Ian. By the Spear: Alexander the Great , and the Rise and Fall of the Macedonian Empire. New York: Oxford University Press, 2014.

Geography.

India is its on continental plate which is slowly but very surely ramming its way into Eurasia and has thrown up mountains on basically all sides:

https://en.wikipedia.org/wiki/Indian_Plate#/media/File:Himalaya-formation.gif

So, as a result of these mountains and the deserts and jungles they create in their rain shadows, there are some very non-trivial physical barriers between India and the rest of Eurasia including the the Indian Ocean itself, the Himalaya Mountains, the Hindu Kush Mountains and the Baluchistani and Thar Deserts.

So, you and your army want to get to the Indus Valley - well, the Hindu Kush and Baluchistani Deserts of Afghanistan are in the way and more importantly their warlike inhabitants. Better conquer or co-opt them. Okay, so you've conquered Afghanistan (no mean feat at basically any stage of history) and have forced the Khyber Pass into the Indus Valley. Well, now you are in yet another bottleneck formed by the Thar Desert (The Persians pretty much stopped here by the way). There's basically only two ways around it - what would later become the Grand Trunk Route north of the desert and the Gujarat route south of the desert. More choke-points, but, okay, you've surmounted these barriers too - on to the goodies of the Gangetic Plain. Except now your bows are de-laminating in the unaccustomed heat, your steppe/plateau horses can't find forage and are scared shitless of the elephants, your soldiers are dying of malaria and are frightfully far from home at this point. So yeah, not impossible, but if even Alexander and Genghis couldn't seal the deal it's not going to be easy.

So it's really no surprise that India was rarely if ever conquered by invaders from outside the subcontinent that didn't initially have a power base in modern Afghanistan (e.g. the Kushans or Mughals) and the primary exception to this rule (i.e. Great Britain) had an absolute mastery of the seas and didn't have to descend into India through all these natural barriers. That said, even industrial era Great Britain had major issues trying to surmount the aforementioned natural barriers from the opposite direction when they attempted to invade Afghanistan.

The question presupposes that there was an entity called 'India' that could be ruled in it's entirety. From after the time of Asoka in the 3rd Century BCE there was no single ruler of the entire Indian subcontinent (and even the Mauryans did not control the southernmost part) until the British rule. The point being: there were no indigenous rulers of all of India as well. Even the nation of India as it is today is actually a fractured portion of the British India, with Pakistan and Bangladesh (and the Himalayan nations) broken off from the main part of the subcontinent.