I think Reactions Channels are good only when done right, and unfortunately about %95 of React Channels out there aren't doing it right.
I've done a few React videos myself just trying to garner new subs, and just so I can say I at least tried it. But it almost felt too much like selling my soul, and I'd rather spend time putting thought into my own creative videos than a few hours shooting, recording, and editing something even I wasn't that much a fan of myself.
But still, I do feel an occasional React video isn't all bad. Honestly I find it rather interesting when my fave YouTubers do React videos on the sole basis I've always been super fond of learning about them as people, and not when they're "on" and entertaining. So to me, it's kind of interesting to see their genuine reactions to things. Helps you gauge who they are as people.
But %100, occasional or not, React videos should always contribute to the video somehow, or else I literally could have watched the video on the OP's channel. And I always feel like unless you get permission, or the OP makes it abundantly clear they don't care, you should never post the entire video in your own video. Takes away from the hard work of the OP.