The situation you describe is sadly a universal one, and not only in open source. The way I see it, is that ImpressCMS can only take responsibility for the core and the core modules when it promises an upgrade path. We cannot take responsibility for all the other modules that are out there, whether they are still supported or not.

Your point about what it takes to make a module 2.0-compatible is a good one. I understand that Mekdrop made every effort to keep backward compatibility with the old modules, but those old modules will only offer the old ways of working. Once we have a more stable 2.0, the documentation should be made available, firstly on how to create new modules from scratch, and after that how to make existing modules compatible.

Keep in mind that we are bridging multiple gaps here : ImpressCMS 1.4 -> ImpressCMS 2.0, but also PHP 7 -> PHP 8.x. It is very well possible that modules are simply not compatible with the new PHP version, before looking at the ImpressCMS version.

We will need to do extensive tests on upgrading module versions, and define a general upgrade policy.