Exactly. I find myself wondering why Stripe is still in the picture, seems like they're doing the easy part.

We use the above-mentioned things, and they also take care of providing a UI where customers can change their plan, cancel it, download PDF invoices. Upon plan changes, they deal with proration. They send dunning emails for failed charges and cancel the plan after N retries. You can set up coupons, discounts, trials, credit, refunds, welcome emails, etc. through them.