Well, it's their choice. If you care about the process - i.e. it's a hobby for you, or a spiritual experience, then it's totally valid to go without AI.

But I feel it's a bit crazy not to use any AI assistance to develop real code these days, if you care about outcome. You can get to result much faster, and have a higher quality solution, if you use it right.

The problem for open source is low quality slop, not AI assistance. Not sure what's the solution though.