It depends on what you mean by viable. Plenty of projects have fixes and features that live in forks and solve real issues for real people. Plenty more have bits and pieces copy-pasted into other repos, forming the basis of a new project. Rather than focusing on the expected viability of a fork, the real value is that it's possible at all to have one.

You can't make other people do stuff for you for free. Sometimes, as you've relayed your experiences, you can't make them do it even if you pay. At least open source gives you the option of fixing it yourself, or paying a third party of your own choice to do so.