A Pi4 does the job well too. They can be had noticeably cheaper than Pi5s ATM, if you don't have the luck of having a device lying around ready to be repurposed, and even the 1Gb models are plenty sufficient.
A Pi3 may suffice even, that is what I ran Kodi on before upgrading it to the Pi4, though the lack of hardware x265 decoding support is a limiting factor there (IIRC it'll manage 1080p in software, but only if you have some good cooling installed otherwise things get very skippy after a short while as thermal throttles kick in).
I’m pretty sure Pi 4 struggles with 4k decoding. It can work but is less than ideal. I also wouldn’t recommend buying a new Pi these days. Prices are insane.
Most of what I watch is 1080p (I don't really have 4K capable eyes!) but it definitely plays 4K 265 well.
Only 265 though, the hardware support for 264 is limited to 1080 so 4K there means software decoding which I imagine being a problem much like 265 on the Pi3. It is pretty rare to see 264 used for 4K content though, in my experience.
A Pi3 may suffice even, that is what I ran Kodi on before upgrading it to the Pi4, though the lack of hardware x265 decoding support is a limiting factor there (IIRC it'll manage 1080p in software, but only if you have some good cooling installed otherwise things get very skippy after a short while as thermal throttles kick in).