Taking into account the route, tasks, and team cast, here are my RAW thoughts (not based on editing) on the post-UB seasons excluding the current TAR24:
TAR19: This season featuring the first ever double-elimination at a single Pit Stop had high promise. The route delivered with exclusive firsthand features of new countries such as Indonesia, Malawi, Denmark, and Belgium, but stumbled with the tasks. Remember the predictable disassemble/reassemble Roadblock in the second Thailand leg? The cast was decent, but had a dry sense of personality. In my opinion, Andy & Tommy trucking through tasks and Bill & Cathi's surprise finishes saved this season.
TAR20: This is the last season we've seen teams travel to a newly visited country (Azerbaijan) and it was a drama-filled run indeed with the notoriety of Brendon & Rachel loudly on the loose. The route in the first half of the Race was really good with a diverse amount of locomotives and regional areas within a country. Tasks happened to be quite interesting. However, the last half of the race starting from Tanzania went downhill especially with the Hiroshima-Osaka, Japan visit that could have been easily enjoyable (didn't like any of the tasks, especially the Japanese game show rehash). Teams this season each had their dominant traits whether physically, mentally, or verbally. Like what Phil stated in his pre-season cast assessment, any team had the ability to be champions.
TAR21: Based on editing, the first season to not feature a new country proved to be a turn in the wrong direction. However, based on raw scenes, this could be a decent race. The route was marginal since the first 2/3 of the race stabbed the season with strictly airport to airport locomotion. As for the tasks, most have promise. Casting this season happened to be very interesting with many regular-appearance folks, interesting semi-celebrities with key personalities, and two teams with rolling luggage like Maria & Tiffany.
TAR22: A season with a new special region, but no confirmable new country. The route had a steady flow of locomotion, but the tasks were generic and one leg happened to not involve any cultural or historical reference to New Zealand at all, but rather Chuck & Wynona-land. I'd consider this season as ethnically diverse, but the cast, like TAR19, had dry personalities just scratching the surface of their real hearts.
TAR23: Like season 21, this race featured zero new countries, but had a route that had hope. I have seen better tasks on the other hand. (Like seriously, stand like a statue? That's what they've come down to?) Most of the teams this season had dominant personalities such as pro athletes and athletic heiresses, perfectionist doctors, and friends and family who work well together. This season happened to be one of the few that actually had flavorful personalities, whether sweet or sour.
RAW SEASON RANKING (Best to Not-So-Great): TAR23, TAR22, TAR20, TAR21, TAR19
WITH EDITING RANKING: TAR22, TAR19, TAR23, TAR20, TAR21