I’m just getting to my first VO2max workouts on my new smart trainer (Kickr Core). On high power intervals, at least for me, I’m finding the trainer behaves better if I slow my cadence just a few rpm before the resistance hits then hit the power but not until I feel the resistance go up. The key is not anticipating the power and waiting to feel the hit before accelerating. If you start spinning too soon, it takes a decent chunk of a short interval to catch up. I find the “establish your cadence early” tip works great on longer FTP or lower intervals but not the short high power stuff.
Also, things may not be as bad as they seem. Remembering back to my dumb trainer days (a couple months ago . . .) it still took a second or two to shift and get up to power unless I was cheating and starting early and/or going way over the target for the first second or two (and if you are use to cheating that way, it will screw up your smart trainer intervals - see above). And, I am doing exactly the same workouts I did last year and in comparing them, overall I am generally putting in more KJs with the smart trainer than what I did on the same workout on a dumb trainer. There is always the odd interval where you don’t nail the target, dumb or smart, but over an entire workout, the smart trainer usually wins.