Subscription models only make sense for an app/service that have recurring costs. In the case of Lemmy apps, the instances are the ones with recurring hosting costs, not the apps.
If an app doesn’t have recurring hosting costs, it only makes sense to have one up front payment and then maybe in app purchases to pay for new features going forward
Bug free is not possible, but there are certainly degrees of bugs. If I pay for software that is supposed to balance my checkbook and it has errors in the math, I would expect those errors to be fixed or my money returned. If one of the buttons is 2px out of alignment, it’s not a big deal. The software should at least functionally do what you paid for it to do, without any additional expense. IMHO.
With such a black and white view of bugs, sure. Eith how bugs work in the real world, it’s a lot more complex than that.