We (mostly) don't regard the foundation myth is true. There's one Italian archeologist whose name I can never remember that thinks Romulus was a real person, but that's about it. Among the kings, there's an argument that Servius Tullius was historical, but I think it's fair to say it hasn't got a lot of traction.

If you were to look at one of the newer textbooks covering the period like Cornell's The Beginnings of Rome, you will see the archeology placed against the literary evidence, and you will see it tells a very different sort of story. The area that became Rome was occupied well before the 8th century (the traditional date of founding), and Roman historians projected the unique elements of their state back into an imagined past that we don't have evidence for. Cornell even argues against a period of Etruscan domination, seeing instead the Orientalizing period as one of exchange and synthesis between Etruscan cities and a thriving Latin culture in Rome.

The real historical value of the stories of the regal period is that those are the stories the Romans told themselves about their own past. Romans both used those stories to provide context to their own time, and changed those stories to suit their contemporary needs. So if you compare the stories of the regal period found in Cicero's de Legibus and Livy, you will see kings with slightly different names, slightly different stories (Cicero insists Numa didn't and couldn't have talked to Pythagoras), and a different sort of emphasis. While Livy describes a kind of collapse of royal virtue in the Tarquin regime, Cicero is attempting to show that Rome is the best possible state (as opposed to Plato's imaginary state), and that each king contributed institutions and traditions necessary to the preservation of that state - and it's important for Cicero that those institutions and traditions are native to Rome and not imported from elsewhere.

Why do youtubers tell the story of the regal period the way Romans did? I think there are a couple things going on here.

First, many youtubers are simply not familiar with recent scholarship. I think just about every youtuber that's covered the end of the Republic discusses both the 2nd century Land Crisis, and the Marian Reforms, neither of which scholars today think were real things. Rosenstein published his book debunking the Land Crisis in 2004; I was exposed to it in grad school in the late 2000s. If you're someone reading pop history or classic studies like From the Gracchi to Nero or The Last Generation of the Roman Republic, you're going to pick up those old ideas.

Second, telling the story of the Latial culture interacting with the surrounding Greek and Etruscan cultures to develop a mature, sophisticated Latin culture over the course of centuries might be interesting in a technical sense, but it isn't a story with characters, plot, or themes that most people can recognize. The Romans wrote themselves a past with very interesting characters who do strange and extravagant things. It's a lot more fun to tell, and to listen to, than something about broken pots.