-Unnecessary duo riders that do nothing (Kabuto)
Agree with with this, but have to disagree on your every single other point.
-An ultra super serious tone clashing with cartoony humor (W and Gaim)
Subjectve. I personally found Build humour incredibly refreshing after literal years of godawful Den-O inspired "jokes". Build was hit and miss in humour department, but I did find one of the more funny seasons in the franchise.
I would also recommend you to rewatch Drive, if you want a definition of "bad tonal shifts".
-Lacking monsters of the week (Gaim)
Monsters of the week in "Phase 2" Kamen Rider have been good twice exactly. First instance was W and second was Fourze. Other than them, there is not a single "episodic-driven" season in the last 10 years which wouldn't drastically improve if you remove them. Not that formula itself is bad, modern Kamen Rider just used it incredibly poorly and some of the worse aspects of modern shows come because of how terribly they usually executed it. Especially ones like Drive and Ghost which relied on story a lot and came off with a lot of pointless padding because of just how much pointless filler they had. Plot-driven approach has its own issues (and Gaim, Ex-Aid and Build all have them), but it leagues above sitting through another variation of "here's your guest character, please care about him for the next two weeks, bye".
Also Build technically had a bit of motw, it's just the show bothered to actually tie-up them with the story this time.
-Tertiary riders that do very little after they become good (Ghost)
Can agree only partially, I'm not a big fan of how Build handled Rouge in general, but I wouldn't call it bad either, and what we ended up with wasn't terrible or anything. Just not nearly as good as it could have been. In case of Grease, character actually improved immensly after he changed sides.
-Doppleganger of the main hero becomes a red herring (Kabuto)
If you mean Dad Build, he had a place in the story and was important for Evolt eventual defeat. I think final strech of Build episodes is full of problems, but there is difference between being an underwhelming story element and a red herring.
-Constant drastic costume changes to the point where base form is never used (Ex-Aid)
And Kiva. And OOO. And Ghost. And Wizard. And Den-O. Riders have been doing this for ages. Toy-gimmicks aside (Build isn't really an offender here as well, it's more of an issue with the whole franchise), characters prefer to use stronger forms. That's development. I never understood why people have such a big problem with this approach. Hell, Build literally calls it "evolution", since characters raise their powers constantly.
-Trying to shove in unnecessary politics (Faiz and Gaim)
Both Gaim and Build had incredibly relevant politics. Build's issue that a lot of it came off underwhelming, but they were important. Show's literal premise tells you about country's separation into three factions. How are the politics unnecessary?
-Questionable camera work trying to hard to be artsy (Kuuga and Agito)
Name a season with better camerawork than either those two or Build than.
I hope you don't mean Koichi "look at my shaky cam and long explosions" Sakamoto.
I don't think any season looked more "alive" than Kuuga (even though CGI was so bad), but Build has a lot of decent shots.
-Random tonal shifts (Hibiki and Den-O)
I refer you to my first comment about Drive.
-Drastic focus on the main villain where everything else takes a back seat (Ex-Aid)
Partially agree. Overall focus on Evolt is an issue, but Build spends a lot of time on the main cast and there is not a single character from Sento group who doesn't get at least some development. Grease is a standout from me, since I didn't really like him all that much during his introduction arc, but he really shone through near the end. His final episode was leagues above actual finale.
-Little build up to anything (Faiz, Hibiki, and Den-O)
Build's problems lie in resolutions and payoffs, not builds up. First arc specifically takes a lot of time to properly cook Banjou as a Kamen Rider and we see his hero journey in details. I don't think there are many things in Build that felt like they came out of nowhere (Rouge's weird character shift is the only thing I can think of) Even most of stuff I dislike was properly set up at some point in one form or another, If anything, I often hear people complain that plot twists are predicatable.
-Base form somehow has a chance against the main villain when it should never (W and Ex-Aid)
Every single Rider debut since W had weird stuff like this. In Build's case they sort of gave an explanation, even though it wasn't a particulary convincing one. Then there is stuff like Hazard Levels and their role in the story and balance of power.
But again, I don't get why Build specifically is guilty of this.
-Useless female side character only there for humor (many entries, but W did this the worst)
I don't remember any useless female characters in Build at all (unless you count Vernage, but it was mostly because of production issues). Both Sawa and Misora were relevant to the story and had a lot of character dynamic with male cast members. Sawa perharps less so, I give you that, but if they were useless characters, than every single female character in Kamen Rider after Tackle ever was useless.
-Lackluster final battle (Hibiki and Decade)
True, but it's nothing new for the franchise. Only a few shows had actually satisfying finales. And compring final battle to Decade and Hibiki? Seriously? At least comare it to Wizard, OOO or Drive. Build's ending falls into "eh, that happened" category, but at least unlike Decade and Hibiki, it actually freaking happened, had big ideas and was unconventional in some ways.
-Forced drama that served nothing (Ryuki and Blade)
Most of drama in Build served a purpose. It did relativly better on that front comapred to Gaim (Micchy stuff aside) and 555 and much much better compared to Kabuto, Den-O, Kiva, Wizard, OOO, Ghost or Drive. Some of it was cliched and by the numbers, but show mostly managed to tie drama to character development.
-Putting in multiverse theory without much exploration into the idea (Decade)
They did give it an explanation which makes more sense than anything Rider multiverse offered so far.
-Atrocious music (Kabuto and Ghost)
So which shows do you consider to have good music? Ghost OST felt great and inspired after years of samey hi-tech pop music.
Build music wasn't as bad as Ex-Aid (with its two or three music themes constantly playing), but it wasn't all that memorable either. I personally found it okay.
-Slow pacing (half the heisei series)
That's downright untrue. Build has story stuff happening in almost every single episode. Accusing it of having a fast pacing I can understnad, but slow? It's probably the most story-driven show in the franchise, leaving behind even Gaim with Ex-Aid.
I personally think that OOO is the worst Kamen Rider series by far (unless you count The First/The Next movies), but I don't think even I can go as far with OOO as you went with Build.
That's your opinion and all, but you probably need to give it a bit more context if you want others to take it seriously.