I'm guessing that's because you're using software decode? If you use HW decode it runs wonderfully in my experience. I could play raw 1080p h264 or VC1 Blu-ray rips over the network just fine**. You have to pay for VC1 and MPEG2 IIRC

otherwise it will try to play in software which is no good. This was an rpi3 with Kodi on Raspbian.

Interestingly I believe they removed MPEG2 and VC1 HW support in the 4, so those files play better on a 3 than a 4. But if your media is in h264 and you use a supported player it should work great on a 4.

** I think NFS worked best, and of course over Ethernet. Maybe http also worked (iirc samba would stutter occasionally).

So you're comparing the new pi with one 2 generations back that runs at 1/4th the performance and assuming they work the same?

Well it isn't meant to be a gaming PC. Poor gaming performance seems an odd thing to complain about.