I don't think the show has become too convoluted or confusing, I think it's just become too self-indulgent. And in that self-indulgence, they keep trying to expand the scope of the show and its characters, and it only leads to more trouble. It runs into cliches and stale tropes, dead ends created by poor writing, and an overly bloated premise.
The first season works because it has rails. Both in terms of setting/plot, but also in terms of thematic reach. The show is "confined" to the titular Westworld. The themes of post-humanism, gnosticism, and social inequality all work together and serve the same goal. While it makes allusions to the broader world, it doesn't burden itself with trying to explain exactly how this technology fits into every other technological development that happened in parallel. The characters all have their place (their loop, if you will) within not only Westworld, but also the plot of the season. Every character serves a defined role. They're all meaningfully placed. We're presented multiple, parallel examples of AI achieving sentience, each with their own wrinkles and complications. And there's also Anthony Hopkins there to deliver the philosophical monologues that tie elements together, and Hopkins can do so in a way that feels organic to his character and the plot.
The later seasons pick up additional themes and plot points like a snowball rolling down a hill. "Oh, it's about personal privacy." "And now its about digital vs physical consciousness and the concept of digital immortality." "And now it's about big data." "And now it's about human autonomy." They try to tie them back to the concepts of free will, but it's done in a ham fisted and obvious manner. By season three, it's like watching a 10 hour long episode of Black Mirror (and Black Mirror episodes are already often far longer than they really need to be to communicate whatever point they're making). They writers keep trying to figure out how this technology would fit into a broader society, and end up contradicting themselves as they expand the scope further. Characters that were once important become loose ends that the writers force back into the plot without real purpose. The once impactful revelation that a character is a host becomes cliche very quickly when re-used (heck, even after the Bernard reveal in season 1, Maeve and Felix have a scene that is used to re-assure the audience that the writers now how silly it would be if they re-used that plot element - only for the writers to immediately re-use that plot elment in season 2). After the success of season 1, there's nobody left to tell the show runners "No" and to reel it in back to the core elements that made the show work.
It also suffers from the fact it used a non-linear format in its first season, and then switched to a more linear format in subsequent seasons (as its exceedingly difficult to keep a non-linear format going beyond one season) and suffered from it.