A friend and I have been running a private Matrix server for almost a decade now, it's very lacking in comparison to what the average chat user (especially discord) is used to.

No custom emojis, no self-chat, embeds are inconsistent (e.g. encrypted rooms), multi-image uploads aren't a thing in many clients, adding text when sending an attachment isn't a thing, just to name things we've run into over the years. Most of these have been brought up to the devs many years ago, only to spend forever in spec hell and never actually make it into a release.

We're just tolerating these, because we explicitly moved off discord to have control over our data, but being tech savvy we can handle this. It's nowhere near good enough that I could use it with less savvy people.