Isn't that a false dichotomy? The package repos from Linux distros are basically open-source app stores (in the full sense, only those that support payment are).

With regards to SaaS, nothing prevents open source SaaS software that can be set up for multiple small to middle-sized-user bases. One could argue that things like phpBB is exactly that. They might even connect to each other to form a larger network... I'm still hoping for a major breakthrough in this area.

You may be right. You can not even usually go back to an older version of an application if you want undo some bad decision by the developer. Source code is spotty if you can get at it. Your data is locked in by them on some server you do not control. In some cases they do not even really control it.

I would add the other anti pattern companies use is opensource vendor lock in. They take what would basically be a 'meh' product and put good stuff ontop of it. But to get that 'good stuff' you have to buy their service contract. Sure you are using some open source. But the key bits are still proprietary.

SaaS does an end run around GPL in particular. Unless it is Affero GPL.

And to be frank, a lot of it at the application level is mediocre.

Yes and no. At least in this case the OP could have installed a different version of the app (older or customized), and kept the 20 years of data usable.