You mean I might not have made optimal progress this year because I started with SSB → SusPB → SSB, switched to high volume z2 when the pandemic started, then SSB → custom polarized → my current custom plan?? 
I realized when looking at my calendar that my year could be considered unstructured structure or structured unstructure. 
At least if my FTP remained roughly constant during the year I saw improvement in applying that power with PRs across a variety of time durations.
To the OP: my option might not be very popular, but you’ve been riding for 1-2 years and have had great gains. Cycling / endurance sports are about improvement over years and years, not months. Plateauing for a bit is not a big deal. I wasn’t training with structure at the time, which could have been a cause, but there were long (2+ year) periods where I plateaued or gained 10w on my FTP. At some point you will need to increase stimulus or change things up to make more progress, but it sounds like you have been making other improvements during this period. Again, the progress you’ve made so far is tremendous and I wish I could still make that kind of progress. I hope you find it very satisfying when looking back on it.