Everything the show did well:
-One of the best hero cast in the Kamen Rider franchise, personally my favorite.
-Really charismatic main villains.
-Really great world-building, some of the franchise best.
-None of the episodes feel pointless to the story and most monsters and characters of the week end mattering on some way.
-Cool action overall.
-Really good story for the most part.
-The show has a natural progression of stakes.
-Cool plot revelations/plot-twists.
-Really great directing for most of the show.
-The riders in this show have great dynamics.
-Amazing final battle (aside from some awkward CGI).

Everything the show did bad:
-The Shinobu Katsuragi mini-arc that last from episode 40 to 45 is kinda bad at times and is the only considerable drop in writing quality in the show, but even then it's not that bad because the main cast and antagonist continue to be likeable and there's some really great plot revelations during this arc.
-The main protagonist plan to defeat the main antagonist is really extreme, it doesn't help that it's similar to the plan of main villain of the winter Build's crossover with Ex-aid. It isn't that big of an issue since it's properly foreshadowed, the main antagonist does feel powerful enough to warrant such a plan and it leads to a great bittersweet ending.
-Kamen Rider Rogue's origin and backstory is left to a Blu-ray mini-series rather than happening in the show.
-Kyoka not reappearing feels weird once Katsuragi starts being more important.
-Vernage temporally disappearing from the show makes it almost impossible to care for her character and also negatively affects Misora's character' arc.
-The Hokuto Crows and especially the Hell Brothers feel shafted compared to other characters which removes a lot of the emotional weight of their scenes.
-Sawa at times feel like a plot device that conviniently has or knows where to get what the heroes need.
-Some of the plot developments related to Utsumi are hit or miss.

Reasons for the show's strengths:
This season was originally going to be the last Heisei Kamen Rider show prior to the enthronement for the Reiwa era getting delayed. Due to this main producer Omori wanted this show to be more mature so that older fans that hadn't been keeping with the franchise would be interested. Also due to this, the show had many inspirations of the original season such as focusing on darker topics like war and the rapid economic growth, having a bigger focus on mystery, human experimentation and main rider duo.
The original plan that main writer Shogo Muto had was for Banjo to be the protagonist and for him to take over as Kamen Rider Build after the previous Build entrusted him with the powers prior dissappearing as an homage to the original season where Ichimonji takes over the Kamen Rider title in order to protect Japan while the first rider Hongo leaves to fight another branch of the evil organization Shocker in another country. However Omori wanted the main protagonist to be a physicist which led to the creation of Sento and for Banjo to become the secondary rider instead, but due to wanted to implement both ideas, Sento and Banjo ended up being deuteragonists. Muto is also really great at writing characters which is why the cast is so likeable.
It originally being planned as the last Heisei show allowed the show to have slightly more budget than usual in its first quarter which allowed the show to realize its ambitious setting.
Due to Omori aiming to also reach an older audience with this show, he got slightly older actor than an usual rider show, which allowed the show to have better actors than usual.

Reasons for the show's problems:
Vernage's voice actress Sora Amamiya was with chorditis during the show's run which resulted in her appearing less in the show, which also affected Misora's character due to how connected they are.
Kyoka Katsuragi's actress Hiro Komura had been fighting cancer since 2012. She wasn't able to reappear in the show because in January of 2018 she had to take treatment because the cancer had spread to her lungs and lymph nodes.
Zi-O wasn't originally supposed to exist since Build was going to be the last Heisei show. Due to this Muto had decided the show's ending from the very beginning in order to make crossovers easier (which didn't matter in the end since Zi-O didn't care for this and just straight up contradicts Build's ending).
Some people speculate that the Shinobu Katsuragi plot line was inserted into the show by producer Omori late into the show due to him liking the tropes of evil dads, but this pure speculation and doesnt have enough evidence.

Overall:
Despite the show's quality dropping in the second half, it doesn't drop hard enough to be considered bad and still manages to have a really cool plot and introduces a bunch of interesting plot points throughout the show's entire run. The majority of the cast and this show's world-building is consistently amazing too. So while whether you love the show or not will depend on how lenient you're with the show's problems in the latter half, it still manages to be a great show overall in spite of them. Highly recommend this show to any Tokusatsu fan or if you're into modern shounen anime/manga.