You have valgrind and many other tools instead of "Instruments".
The GNOME project itself [1] has a lot of projects which compete with what you linked. Sure, Apple has a few billion dollars to dump into development every year, so you have to adjust for scale.
None of them has the polish of a full working desktop stack like macOS.
Once upon a time, around 2000-2, I did some minor contributions to Gtkmm.
Yeah. See my other comment: https://news.ycombinator.com/item?id=12854983
I know GNU/Linux since 1995, eventually one gets tired of being part of the 3% desktop usage.
https://developer.apple.com/reference/
Not to mention the related GUI tooling.
Where is Instruments on QtCreator, for example.