Possibly we're just talking slightly at cross-purposes here, yes. I was intending to comment on the idea that the additional features that a service like Stripe offers for recurring billing management were difficult to implement directly -- the scheduled charges, pro-rating of changes, retries on failure, etc. In other words, the extra features that Stripe is apparently now going to be charging everyone for.
I don't think this stuff is particularly difficult to get right, having essentially done it myself in the past. Indeed, I've never actually worked anywhere that directly integrated with a single payment service without at least some degree of isolation/abstraction. (This is also why features like Stripe's recent customer portal are of little interest to us. Directing a customer there to update their details means they can only change them to something else we use Stripe for, but we don't want to be locked into Stripe like that, we want to offer each customer the full range of payment options we support wherever they are.)
The harder things to implement these days, at least in our experience at my own businesses, are the mechanical integration with all the different payment schemes, where you really do need a specialist service that provides the required access, and the tax and compliance issues, where the ever-changing landscape makes outsourcing this aspect of the setup more and more attractive. But you can get the first of those with many different services and you need something like a merchant of record or one of the dedicated tax management services for the second.
Presumably for some types of business fraud prevention is also a big deal, but again you'd get the basic checks with many services that let you charge a card or the like, and I'm sceptical about how much these fancy AI-based big-data-crunching models are really improving performance. In any case, for those of us in more niche markets, there is little scope for someone to defraud us significantly anyway and the risk of anything bad happening has been very low over the years.
So in the end, with the way the industry seems to be moving, I can see an argument for just outsourcing basic payment processing and then handling the automation and tax/regulatory stuff in-house (for example, if you already have a dev team to implement what you need and you're already set up in some other way on the tax/regulatory side). I can also see an argument for outsourcing just about everything to a merchant of record service. But I think the case for the middle ground model that most of the payment services we've been using over the past decade or so operate is getting weaker all the time. And since they all keep forcing us to do major integration work just to keep the same functionality we already had from breaking and putting up their prices, I can't honestly say we've been feeling a lot of loyalty to any of them lately, hence our ongoing investigations of possible alternatives that I mentioned in other comments.