Well so far mostly backwards compatible, tho on the hdmi. It's for drm primarily.
Ok backwards compatibility can be helpful in a pinch, but it ends up just being a frustrating bottleneck in your setup.
Things that have caused HDMI devices to become outdated and therefore undesireable:
Starting from DVD with 5.1 Dolby Digital...
Bluray 1080p 7.1 lossless Dolby True HD...
3D...
ARC...
eARC...
4k...
Atmos...
HDR...
Dolby Vision...
120Hz...
I probably missed some others.
Potentially each one of these could cause you to upgrade your TV, player and AVR.