Thank you for the additional input @dmsnell!
A mentioned earlier, I think the root problem with the server-side performance lies in core itself, and is now being further explored via #59490. Regarding TT4 itself, there may be room for a bit of optimization, but IMO it wouldn't tackle the problem at its root. That said, there are a few instances where I would question the use of patterns to be excessive, for example:
Couldn't all those 6 patterns simply be referenced in the root templates/home.html file? Why the 2 additional "patterns" in between, which don't really add anything AFAIK? Curious if you can share come context on that @onemaggie @luminuu.
I've added links to the 3 more specific tickets related to the performance issues to the description.