They aren't very vendor friendly and their fees are way too high. Little bit like Amazon. they are are consumer friendly at the expense of their vendors.
Isn't this a winning formula because the consumer is the one spending the money? Imagine an opposite approach that was vendor-friendly at the expense of the consumer. I don't think most people would willingly use that.
Back before Amazon, WalMart did the same thing[1] by squeezing their vendors to lower prices and passing (some of) the savings onto shoppers.
[1] https://popularresistance.org/walmart-creates-a-race-to-the-...
Like an aforementioned comment stated above, their dominance is all about consumer convenience reinforcing vendor adoption. If you have an equally smooth payment process to compete against that, it will crumble. Case in point, India and UPI. Credit cards are largely used by the most affluent today, simply because UPI has become so prevalent for general transactions. UPI are actually a much easier way to carry out payments than credits cards are.
But of course, American banking is ages away with even FedNow not having been implemented in any strong form whatsoever.
Stripe is a merchant acquirer and Visa/MC a card network.
The 2%-3% are the total fees imposed by a stripe, a merchant acquirer. The 0.3% is Visa's cut. After subtracting the card issuer's cut, what remains goes to Stripe.