"Hey bro! Here's some 20 year old program! We should totally reinvent it today! It's not like anyone has been working on this exact thing for the last 20 years!". Wtf is with the younger generations obsession with "retro tech"?!? "Look bro, I can do the same thing we can do now, but slower and worse!"
Also Matrix. If you're gonna suggest something, maybe make sure it doesn't already exist.
All these people "rediscovering" old tech like we didn't abandon it for a reason. No, I don't want to build a PC out of old Commodore 64s that barely works and needs to be coded in assembly when I can literally get a mini PC that's 100x more powerful for $120.
XMPP doesn't have link previews or posting, photo albums, even the idea of a picture with caption text us foreign. No comment reaction, retraction or replies. Inline video or video stream, lol no, even gifs don't work. Talking or video chat ? Not even in your dreams.
No wonder the youths hang out on discord
Gajim will have some more of that in the next version, Monocles or Cheogram have more modern features than Conversations and Siskin is very outdated feature wise and you should probably replace it with Monal.
That said it is not true that the three clients you mentioned have none of that. Sure they don't have all of it, and there is some feature mismatch between them, but you are making it sound much worse than it is.
Oh and you can always use Movim which has most of the features you mentioned.