Are you new to GNOME? this is a few years old when Canonical dropped Unity. What was happening was that each GNOME release fixed some memory leaks but create a few new ones, the lag was terrible and when Canonical moved back to GNOME a Canonical developer started fixing stuff, GNOME devs were blaming the hardware for the bugs or were busy with removing features.

https://www.omgubuntu.co.uk/2019/10/ubuntu-improves-gnome-sh... you can google the dev "Daniel Van Vugt" and check his work on GNOME, or you can google "GNOME shell memory leak" , as I said I stopped following Linux stuff (I am still a Linux users) and I have no idea what happened in recent years except the major things like GNOME's reset triggering a new fracture in it's community.

Anway, Canonical was not using GNOME so RH did not avoided paying for better developers because Canonical would benefit. Later when Canonical decided to use GNOME they fixed the major performance issues and memory leaks and put back some of the features the users wanted but designers refused to provide.