I'm starting to feel like hardmode is kind of taped onto the game, and that it's kind of a dead end. It doesn't quite fit in and it just kind of feels.. not as open as it was before hardmode.
Yeah, agreed. hardmode destroys all the "natural" biomes unless you make a point to painstakingly safeguard them all BEFORE activating it. Once the novelty wears off, hardmode actually limits your options pretty much everywhere. It actually makes building in a building game annoying to do.
I've actually been pretty happy with it. I've been running the same world and played heavily for the first 3 weeks or so after the 1.1 patch came out, and 4-5 hours a week since then with my kid. It's been on hard mode for a long time, and still has every biome intact, without having taken any major steps towards conservation. I've just kept some seeds from each one in storage in case they do get wiped out, but they haven't. The world still feels really diverse and interesting. There's a definite flavor of corruption/hallow being a threat to all the more natural stuff, but there are very resilient pockets of natural desert/jungle/etc out there to be found. There's a large jungle area that I'm kind of fond of, because you have to travel a good distance east through hell and then it's just up from there and goes about halfway to the surface. It just feels appropriate that those biomes would cling to survival in remote areas where you can discover them like hidden paradises.
I've finished collecting almost all the endgame stuff now, though. I think it's about time to build a secret base for myself and place traps all over the map to catch all the other people who log in now and then by surprise.