My N=1
I’ve read and listened to all the Seiler stuff. It is clearly at odds with much of the TR philosophy. Regardless of how you define zones or name them, TR’s approach is to go hard at least 3 days a week, up to 6 days a week, while polarized is max out hard days at 2 (maybe 3 for the very short-term) then focus on low intensity riding for the remainder.
A key point that I haven’t seen mentioned above is study structure and the perils of extrapolating results, which Seiler mentions in some podcasts. TR bases much of it’s approach on studies performed over a few weeks (or even a few months), and for these time periods, Sweet Spot is extremely effective. I truly believe that if you become a good Ramp Tester, some of the high volume plans can teach you to suffer like no other plan I’ve ever seen. With this ability to suffer, plus the physiologic gains over a 3-6 month cycle (like a Base/Build/Specialty plan), a rider can blow personal-bests out of the water.
The problem develops when you start trying to string these together over a span of years, which I know has been discussed above. The vast majority of studies (maybe all exercise physiology studies?) in amateurs are done over a relatively short period of time. When these plans are stretched out longer, there are major hormonal shifts occurring that cannot be captured in 3-6 month observational windows. Pushing your body into the red 4-6 times per week for much longer than a year or so can lead to some bad outcomes. I started using Whoop recovery monitoring this year, and it has shed some light on these periods of intensity. I’ll tell you it isn’t pretty.
I will be doing polarized training for the foreseeable future because, for my N=1 (and I know I’m not unique in this respect), it just isn’t kind to your body or your stress hormone systems to push yourself that many times per week for years on end, and I am including anything >65% Ramp Test FTP as “pushing yourself” with full recognition that Sweet Spot can make many people faster cyclists. I’d like to be cycling for the next few decades though, and I feel that more than 2x/week intensity at 10-20 hours of structure per week will inevitably lead to destruction.
To switch gears a bit, I have trouble understanding the dogmatic clinging to sweet spot. TrainerRoad is perfect for a polarized training model because of the profound level of control one can over time in zones, total time per week, intensity control down to the single % level, and the diversity of the interval structures to keep it fun. The workouts are already there, so why is TR loathe to embrace a polarized set of plans? I doubt I would be alone in my appreciation for Chad, Nate, Jonathan, and everyone at TR applying their expertise, incredible user-friendliness, and scientific acumen to a new set of polarized plans to exist right alongside the masterfully formulated current plans.
I’ll be a life-long TR user regardless 
it makes me happy to read this, as some of us were telling you to stop going overboard on training.