I have been a big fan of the show since the beginning, especially the first three seasons. I also agree with all of your comments, including my disappointment with season 5 & its finale.The initial seasons were a breath of fresh air, capturing Adlon's (& LCK's) wimsy & irreverence, telling the story of a minor-celebrity single parent (none of which am I) trying to fumble through (as most of us are) in the 21st-century. Throughout, I celebrated being educated, having my mind expanded, and just going along for the ride. Amidst the overall high level, there were moments of absolute brilliance (note the "Tilted" video that ended season 2 as a prime example), that I was so happy to have witnessed. Even when the story route appeared circuitous, it eventually came back to close the theme, if not completely resolve the topic at hand.
Season 5 was so disjointed - some of which was the result of the pandemic as you noted, and some was the result of creative choices that Adlon made (seemingly) on purpose. Most disappointing to me, I think, was that many of the characters seemed to go backwards. Frankie is still pretty-much the insufferable child she has been all along despite now becoming an 18 y/o, Phyll is back in England with her childhood beau, Jeff is back with Alan after we witnessed a horrible breakup breakdown, Rich is re-marrying Sunny (really???) - the only relationship more toxic than Jeff & Alan's. Finally, Sam is now the unapologetic, irresponsible creative/social-justice-warrior who can spew her "shit" everywhere (another overarcing them this season) while her stable, good-&-perfect brother Marion picks up all the pieces for her. She's basically given up trying to be "better" (see what I did there?). The only character I felt compelling this season was Max, who's arc saw her develop & grow (painfully so) into a real adult (I just wanted to give her a paternal hug). Most of the rest this season was self-indulgent filler, including the un-creative, nearly verbatim rehash video opening of the finale "Woke Up Looking" (the original artist with whom Adlon apparently connected because her own real-life daughter shares the same first name). Whew! I feel "better" now (see what I did there again?). I'm sure Adlon doesn't give a rat's patootee what I think so...
TL;DR - loved the show, not so much the final season or finale.