I felt the same about The Undoing. It started off with a lot of momentum, but (I) could feel where it was going and I gave in and just moved on. When i read how it concluded, I can see where you're coming from Blue.
If I could be so forward as to suggest a show or two, my biggest surprise maybe ever-(on showtime anyway) is a show called I'm Dying Up Here . WOW. It may feel a bit or even very-slow in the initial episode or two sure, but after it gets going, its just plain AMAZING and very much a diamond in the rough, imo. The performances, writing, setting, are all top quality, and as surprising as it is to me, its within my top three favorite shows ever and one that was also canceled too early (Deadwood and Rome being other favs). It starts a bit dark, or imo has real life grit, but its worth the time investment to give a few episodes. Its a *HIDDEN GEM*, I tried to not watch it for a while before giving it a try, it is a stellar show.
Another GEM, for those willing to do subtitles/dubbing, Babylon Berlin WITH dubbing-ON and yellow subtitles ...,(my top tip for all show watchers is yellow subtitles, as it contrasts much better at night, and with most shows and doesnt pop @ you quite like white on black box). Babylon Berlin starts dark and weird, and also a bit slow-ish, but with dubbing which is of stellar quality, and i believe dubbing voiced by (mostly) the actors that played the roles, the show is unique and one-off. The dubbing gives this noire feeling to the amazing setting, music, and visual effects. Also, the creepy dark intro is the best show intro music and presentation ever,imo. An intro that actually adds to the show very nicely. The creepiness of Babylon Berlins historicity and the feeling it evokes...unparalleled, and the intro captures and adds to it nicely.
I enjoy a good history-truth-laced-entertainment, and Babylon Berlin is amazing throughout, and has managed to stay pretty good even into season 3, a feat in itself with a lot of shows these days(imo).
Classic Courses is my favorite Amazon Video channel. Great stuff, and soo much variety too! BIG recommend checking out the free trial for that one! Amazon's free trials for many channels makes giving an episode or few an easy option.