The trade-off between time and intensity also probably depends on what type of events you are actually training for.
My low volume, polarised plan this year has worked very well for short, high intensity Zwift races, where I am now a strong Cat B, vs a borderline Cat B/C for the last couple of years. But I’ve fallen a bit short on the couple of timed century sportives I’ve done so far. My endurance beyond 3 hours drops off significantly more than it did on a higher volume plan. So I’m slower on century rides despite a higher FTP and VO2 max power.
So I guess I need to add in more low intensity volume if I wish to improve my endurance over 4+ hours. Not a big surprise really. But otherwise I’m quite happy with the bang/buck of my current training plan. To be fair I’ve been skimping a bit on my Z2 rides in this polarised plan or subbing shorter rides in Z3. So I need to be more strict about completing those longer Z2 rides on plan. I have at least 3 more century events coming up so hopefully I can improve my endurance.