"Who knows how many of these companies could grow into something bigger without the pressure of generating a return for early investors in just a few short years."

It seems to me like this is part of a more general trend - namely that a lot of startups might do well to figure out how they can make a profit first, instead of going the venture/acquire/cash out route. It's not incubators that are hurting startups - it's that a lot of startups should probably figure out how to be profitable first.