Same old story, too much support requests and bad actors making it hard to make money off opensource.
This is one case where we really should support the original product, you can buy a perpetual licence of a pittance and they just 2 guys chugging along.
LibreSprite has 5000 commits, 30 in the past year whilst ASEPrite has over 10000 at this point.
The person you're replying to was making a clarification on the license, not arguing about the validity of changing the license or charging for it.
Libresprite is an important project because people can fork it and learn from it by extending it, and submit those patches upstream, regardless of how active it is.
I think aseprite is a perfectly fine project, but where possible, I like to use open source tools rather than proprietary tools.
I have paid for Aseprite, but on many machines I just install the old GPL version, usually available as a package. It is fine for most tasks, even if the latest version has many improvements.
A fork of the old version to have a slightly better version conveniently available in package repos would be nice. I don't think it has to catch up with Aseprite to be useful.
It's good to have open source software.
It's good to support honest and high quality proprietary software.
Aseprite offers the latter good, this offers the former good.