I use an old wifi router, a raspberry pi 4, which accesses an old NAS on wifi, which plays to the TV via wifi. I have a mix of h265, h264, vp9 in various formats from over the years.
I don't have any problem with streaming (except with exoplayer on my Android phone which sometimes, not always, wants to transcode vp9 YouTube downloads).
I've even used it from outside the network in relatively slow internet and it's okay.
It's got it's issues sure, but not clear what that guy is doing wrong!
May I ask what you did with your GPU vs ARM memory allocation?
I have 320M for GPU. Seems to work fine, but not sure what is ideal.