These two threads are brief but they cover the main points. Gallipoli was attempted against a foe which flat out did not have a navy which could possibly contend with Britain and their armies were distinctly inferior to the invading forces...and it was still an utter disaster. With an invasion on Belgium via the sea or even worse on German soil they would have to contend with the sizable German navy which is not conducive to a naval invasion.

From one of the linked threads:

Later in November 1914, First Lord of the Admiralty Winston Churchill put forward his first plans for a naval attack on the Dardanelles, based at least in part on what turned out to be erroneous reports regarding Ottoman troop strength. He reasoned that the Royal Navy had a large number of obsolete battleships which could not be used against the German High Seas Fleet in the North Sea, but which might well be made useful in another theatre. Initially, the attack was to be made by the Royal Navy alone, with only token forces from the army being required for routine occupation tasks.

First Sea Lord John Fisher opposed the campaign and instead preferred a direct naval landing on the north coast of Germany, but Churchill won the argument.

Essentially the British never wanted to decisively engage the German fleet because they had a large but also largely out of date navy and didn't want to take the chance of actually losing. A naval invasion of that kind of magnitude requires naval supremacy which, even after the Jutland, was arguably not achieved. There is also the issue, obviously, of logistics. Airplanes were still in their infancy, landing crafts to my understanding did not exist, automobiles were only used in a limited fashion and armored support was hardly in its WW2 blossoming stage.

It would be, essentially, dropping a couple hundred thousand men behind enemy lines (just a walking distance from the enemy lines, at that) and hoping it works...in a war in which very few men actually manned the trenches but significant amounts (millions, at that) of local and strategic reserves were kept well behind the lines to respond to enemy action wherever it came. So this kind of naval invasion, without aerial bombardment in any meaningful way, without WW2-styled armored assaults, without the mechanized logistical support of 20 years later would require a significant amount of men to work with logistical support frankly not feasible to land barely behind the enemy lines only to be met by an equal or greater amount of local/strategic reserves who did not have to receive supplies across the English Channel.

Basically everyone in the British navy was armchair generaling about a glorious seaborn invasion but it was just not feasible with the circumstances and was rightfully scrapped. It's not just about getting a bunch of men there it's about getting a bunch of men there and then bringing them a steady stream of reinforcements and supplies.