I don't know the Pi4 architecture deeply enough to offer an opinion on it, sorry. Ask me in a year or two and I'll likely know it a lot better.

Well, they fucked up their implementation of USB-PD with a rookie-level mistake, it took ages for them to support booting off USB, the 5V rail is noisy...

Raspberry Pis were initially just a way for the Pi foundation to help Broadcom sell SoCs nobody wants anymore but they still had lots of stock/tooling for. Sort of like "hybrid" bicycles are how bike manufacturers milk more money out of hardtail (non-suspension) MTB frames.

It's almost the same overall architecture, just a lot of pieces have been upgraded to be wider and faster, and some peripherals added.