One thing PayPal does well is have all the features you 100% depend on, already running well. The UX is kind of terrible, but it's at least all there. As a PayPal purchaser, I can enforce a specific shipping address, or a specific source payment method, change it constantly at will, and the seller mostly can't mess it up (PayPal enforces it on my behalf). I can sign up for a subscription, cancel it, all from PayPal's side, and the seller literally can't control that experience or block me from doing that (PayPal enforces that on my behalf too). I can even dispute a transaction with one click (although I've never needed to, so I don't know what happens after that).
I also have a Visa, MasterCard, Amex, Discover, and Simple, and Venmo. Some of these other credit card merchants or cash services have parts of these pieces half implemented. (There are 'fake/disposable' cc numbers and such that try to replicate the 'cancel anytime' thing. You can definitely call a credit card company to block future transactions from a specific company). But to my knowledge, no one else actually has the whole minimum-featureset-for-purchasing figured out and accessible with just clicks online. PayPal does. And they've had it, consistently, for almost a decade.
---
So, as a person who writes eCommerce stuff all the time, I get why folks in the industry is sick of it. (It's duplicate steps, we always have to do "real credit cards" merchant, and also a separate "PayPal" integration)
But as a purchaser, I always prefer the PayPal option, rather than handing over a Credit Card to their Stripe/Square/whatever merchant service -- especially for anything with recurring billing. I get why other folks prefer it as well.
I do look around once in a while, for what the alternatives are, but so far PayPal is the only service that lets me run my business from a passive web page. I don't even have my own URL. Every other service seems to have a tutorial showing me what code to install on my server, but frankly hosting and maintaining a server (at home or in the cloud) seems like it would add a dimension of complexity to my business that I don't want to deal with. I certainly don't want to be responsible for handling and storing my customers' credit card numbers and similar data.
I also think that the customer protections are beneficial, since they give people the confidence to buy from a relatively unknown seller.
On top of that, they have a deal with the USPS that lets me generate a first class shipping label, which isn't even available at the USPS website. What I save on postage more than covers the PayPal fee.
I mostly use PayPal when there's some kind of promotion that gives me an incentive, such as extra credit card rewards, or a cash back offer. I think a lot of people find it convenient to use PayPal for ecommerce because they don't have to get their credit card out, just enter their PayPal password.