Honestly.. this feels like needless purity-testing to me.

Yes, this person earns a living on YouTube. That is where the people are and that is where the money is.
But that doesn't mean they would be entirely unwilling to switch to alternative platforms once that becomes economically viable.

And in the meantime they are helping by informing people that alternatives exist, and where to go to find these alternatives. That will hopefully help European platforms grow to a point where "influencers" can meaningfully switch over

Edit: I'm not a fan of purity testing, because it is generally counter-productive to actually achieving your goals.

You need to meet people where they are, and not expect them to fully fit in with your ideal standards right out of the gate.
That is how you get people on board with what you want to achieve.