Yeah, my perception is they're useful, especially if done when you've already got a few days of fatigue in your legs. I've also started doing two Zwift races on some days, which really twists the knife if you do an hour or two of riding between events.
Training crits have started in NEBRA but I probably won't be racing outside until April as it is hard to justify driving 2hrs each direction for 50min training crits. In the meantime, Zwift races are giving me the kind of 30sec-1min punch I do not usually have until late May or June. I still can't sprint at all indoors though.