Reaction images are unfunny tripe that only exist to clutter a thread.
I don't know if this take is actually 10th dentist but I've never seen anyone complain about it, so it's probably not on the minds of most users. This problem plagues subs that generally skew younger and it drives me nuts.
Reaction images are completely useless. There is no need to signal to random people on the Internet that you understand the meaning conveyed in a meme and are capable of reacting to it as expected. I start seeing red if I open a thread and at the top is a gif of Kevin from The Office laughing or 50 consecutive comments that are just iterations of people or animals looking concerned/disgusted/awkward. It's boring, low effort, and contributes nothing to a thread. I swear most of these are just people pulling up their image gallery and uploading the first thing that's even remotely close to a valid reaction.
I've seen posts in subs asking for mods to enable image attachments for this purpose. It's baffling to me why people would willingly want this shit in their feeds. It only helps Reddit inflate their numbers to show how many engagements posts get.
This problem isn't too bad on old.reddit because every post just appears as "Image" and is easy to ignore but on mobile they vary in size and are just distracting when you're trying to sift through a thread to find if there are any discussions being had.