Nice review. I can't say I completely agree with it, but I can certainly understand where you're coming from. I always took the bits with the lizardmen (and similar sections in season 3 with the village, etc) to be primarily world-building. Inevitably that makes the anime feel a bit weak in places in comparison to the light novel, which is more continuous (as it's broken down by volume rather than by season).
Ainz being OP is true, but then isekai light novels are largely power trips of varying degrees. What Overlord tries to do, I think, is make you sympathise with the other side more than with Ainz. That's probably why they have such extended sections from the points of view of Ainz's "enemies". And the tension for me has always been in seeing how far Ainz has lost his humanity. Early on he seems to still be fundamentally human, then by the end of season 2 he doesn't seem to feel any empathy for them, using them entirely to his advantage. That just gets even more extreme by the end of season 3.
I think some of the comments are fair, I still love the series and I think it stands out for other isseki dross. Its a shame the CGi is so crappy but the characters and world building are strong enough to get past that
Will still say the whole point of the lizardman arc was to show how Nazarick looks like to outsiders, and to build/develop the guardians growing to be more independent like Cocytus defying an order because he personally wanted a different outcome.
The story isn't about all powerful beings destroying all enemies, but how the world/characters change/evolve/interact with this force called Nazarick.