You lose a lot of single core performance, and TR4 motherboards are also a bit pricier than their AM4 counterparts.

Well, higher end z370 board are not much cheaper and I expect the new z390 close the gap even more

ThreadRipper is great if your tasks are always multi-threaded, but if you're doing anything that sees more benefit from single-core performance (like a lot of games, though this is changing), you're better off with something else.

Don't forget just how many simultaneous processes run on a stock OS install anymore.

More cores/threads are good at least to the point where you have as many hardware threads as software threads.

Even a pile of single-threaded apps running simultaneously benefits from multiple hardware threads.