To each its own I guess. If one likes AVR hub and it works, it works. TVs have been alternative hubs for more than 10 years and many use it in such a way to connect higher bandwidth stream directly.If eARC works for you and you don't need many inputs, then that's good. I think it's just as simple the other way around - in fact in my experience it's less prone to problems.
I don't know if this is in relation to my comment on standards. There is a standard for HD, rec 709. and Ultra HD, rec 2020, the TV switches automatically between the two.
HD signal needs more post processing than 4K signal. It will be much softer and more noisy especially if from HD master (like original Blu Ray). Depending on the processing capabilities of display, one might want to adjust processing differently than for 4K. Then in many cases there is even lower quality signal for a lot of TV broadcast material either through cable or internet box. This will also require some adjustments.
Finally, one would not want to over process high quality 4K signal, but there might still be some relevant settings to adjust depending on the bit rate (stream vs 4k disc) or frame rate.
Displays generally offer one or two film mode or equivalent profiles, so having additional per input and profile capabilities might be relevant to some that feel finer adjustments are needed.