Technology

Proprietary standard that’s worse than modern DisplayPort specs. Adds cost without adding features.

https://en.wikipedia.org/wiki/DisplayPort#Comparison_with_HDMI

Mostly licensing. Every single hdmi port manufsctured requires a fee, and the closedness just holds tech back.

It is a proprietary closed protocol with built in DRM. The HDMI Forum is not consumer friendly, charges royalties to manufacturers for the productiom of HDMI capable devices, and HDMI has no performance advantage over Display Port.

Enemy of your freedom. Doesn't even let AMD support 2.1 on Linux so Steam Deck or Steam Machine cannot support 2.1 with open source drivers! That's why it's officially only HDMI 2.0

The connector is flimsy, will wear out in applications where you connect and disconnect it often and the whole standard is controlled by big tech and they abuse that power to hinder open source efforts.

1. It has it's DRM implementation, that, albeit weak and useless, was designed to manage what you can or cannot plug these cords into, e.g. capture cards. That's probably an advantage for Sony and others.
2. HDMI specs are <10m or bust, so for big rooms or video prod on HDMI you need amplifiers. They may be included in the cord itself, but that makes it one-directional, lol.
3. Not to say that HDMI cords are expensive and you also can't press their ends to the lenght needed yourself, unlike what you can do with SDI cords.
4. No mechanisms preventing them against just popping out from the socket. Anecdotally, I think there's something weird with their construction maybe, that in my experience made metal connectors suddenly come off completely around 5 times this year, while no other connectors suffered that faith, even dumb VGA that are prone to have their pins wrecked.
5. HDMI is rigidly limited to what it can with what standard and has no interesting things going for it imho, at least no daisy chaining multiple displays one after another that DP can.