MacOS Catalina: Slow by Design?

Just switch to Windows and WSL. For most cases, it works just great/not noticeably slower.

There's a lot of bullshit on Windows too but nothing near OSX levels of wannabe big brother shit.

Can't think of a better long term short right now in the market than Apple (and sister cult Tesla but the electric story is at least in the early days so they may do ok)

Windows has SmartScreen and MAPS (which was previously called "SpyNet") turned on by default, on top of telemetry level that goes to eleven and cannot be turned off in consumer editions.

They're not implemented in a braindead way that's being discussed here but they're at the same level big brotherness-wise, if not worse.