Yes, I agree, 10.15.4 was botched, awful.
Tentatively: yes, 10.15.5 does appear to be back on the right track - even though installation was still weird, like many others in the recent past for the MP7,1. In this case, the mac just shut down. No info (typical Apple). Anyways, after re-setting the SMC as usual (because it won't start otherwise), it came up as normal and proceeded to install the update.
Everything seems to be running unusually well (!) and this includes a fairly broad swathe of software interactions: many VIs, audio & video plugs; NLEs, DAWs, 3rd party productivity software etc.
See also,
What has changed in Catalina 10.15.5 and
10.15.5 & 2020-003 Updates.
Still, in my experience of new Apple hardware & compulsory latest OS only support, we'll know when Apple is indeed 'happy' with Catalina when the Pro Apps updates appear on the Apple store - FCPX, Compressor, Motion, additional support resources etc - these have been unusually absent for quite some time. The only pro app that has appeared recently was Logic Pro X 10.5 but I suspect that one is largely unrelated to Catalina, but more about new looping & sequencing features & in any case bought its own new bugs, eg,
Native Instruments.