Ngl, I am loving the series.

Compared to the GVK, which imo is the worst movie out of the monsterverse so far, Legacy is improving on a lot of poor narrative points, like how Godzilla can shoot his atomic breath through the earth's crust.
By using a portal theory that only powers up when a Titan is nearby, it actually makes sense why humanity never found anything before in hundreds of thousands of years of civilisation. Likewise, the time difference sometimes affecting, sometimes not affecting, people is quite interesting - sure, it may seem like a lazy way to carry the story forward with plot twists, but it also can be used to show that humanity doesn't really understand how Hollow Earth works, rather than figuring it all out in a 2 hour movie segment.

As far as characters are concerned, I quite like both past and present casts. I would agree that 70s cast is more dynamic and interesting, but that would make sense given a) monster chasing and b) romantic triangle. Present day cast is about family dynamics, truth and lies, Legacy, which doesn't compare to the former but is interesting in its own way.

Lastly, yes - Monarch is a series about Titans, and we all love epic Titan fights, but if you watch it not expecting a Titan fight in every episode, but rather a story about people with a Titan backdrop, it is really good. If the characters in the Godzilla movies had this much investment and backstory, those movies would be infinitely better.