The only acceptable react channels imo are people who either 1. Have a background on the topic of the video and can provide more info/review the content; 2. People who pause the video and give their genuine impressions on the thing and learn something/are fans of the thing so they gush over it.That's fair, because it's a criticism of the quality of the work, rather than a generalisation.
React content is one of those things that's difficult to discuss sometimes, because a lot of people will see someone doing react content poorly and their takeaway will be that the format itself is a problem, rather than the lack of quality control within it. It's more of a Sturgeon's law situation than anything, there are bad music channels, there are bad Let's Players, and there are bad reaction channels.
Most twitch react streamers just put random videos they don't give a shit about and talk over the video while missing key info and then act like the video didn't address it, and the takes they give are usually the most braindead/milquetoast takes out there just so their audience fellates them.