5 minute power - and especially durations shorter than that - might not give you the real picture if you have actually improved you VO2max or not. Although most of the power is created aerobically, anaerobic capacity plays a big role in these shorter durations.
Personally, I find that hard aerobic training hampers my anaerobic capacity for a while. Yes, that anaerobic power does come back with enough rest and some “sharpening” but it might be hard to see improvements initially. Say for 5 minute all-out effort, you improve your VO2max by 10 watts but lose 20 watts due to lowered anaerobic capacity and thus the 5 minute end result is down by 10 watts. Using just one metric to measure improvement can be quite challenging.
And when the measurement becomes the target, you really have to be careful to not lose sight what’s actually important for your performance. If improving 5min pmax (or even shorter duration) is your main focus, then you’ll probably want to change your training quite a bit.
There’s an excellent thread about Ashton Lambie’s training for sub 4 minute pursuit to give you some contrast what training for shorter distances might look like: Ashton Lambie breaks four-minute pursuit barrier - #21 by AJS914
Also, your VO2max might not be the limiter. Maybe the limiting factor is more on the neuromuscular side? In that case something like strength training, both in the gym and on the bike, will likely yield better results than hammering high cadence VO2max intervals to the infinity.