That’s what new releases are for.
I pay a flat fee to use a specific software revision, say Aseprite 2021. That allows me to use that version and it’s capabilities for as long as I wish for that one fee. Why should I pay a fee month after month to use software with the same capabilities until the creator decides to update it? If a later revision adds enhanced capabilities I am free to decide if I want to buy the new version.
A subscription model does not promote the enhancements that a purchase model does. The creator knows they are going to continue to profit off a subscription regardless of what they add. A purchase model incentivizes them to create a truly better product because they have to make the software worth another purchase.
Sorry, but a subscription model creates complacency. A purchase model creates ingenuity. Subscriptions models arose from greed, plain and simple.