Blech, I hated the whole Clans thing, for a few reasons, but mainly I just didn't like the warrior-centric culture developing out of the remains of the Star League. Sure, it was less predictable than a happy utopian society, but it's just always felt so overdone to me.
Second most, I hated the bump to technology. I didn't mind the Grey Death Legion finding the memory core, but it felt like things came up out of the gritty dark ages way too fast. Too much like a magic pill that solved a big "problem" for the Inner Sphere. I use quotes there because I didn't think of it as a problem, it was a core part of what I enjoyed so much about the atmosphere of the setting.
I liked Battletech a lot more when it would have been a very rare thing to get given a replacement mech if you lost yours. That whole Dispossessed thing, you know? And the idea that mechwarriors were special at least in great part because they had
a mech, this ultimate war machine, to leverage themselves into being the core supporters of their House ruler, their lord, like knights or samurai, to some degree. And like knights or samurai, they were defined by their armour and/or weapon. The idea that a lord could only hold power if he/she had the support of enough mechwarriors, that quasi feudal feel it had in the good old days, was part of what drew me into the universe from the start.
All that just flew out the window when there was this huge influx of lostech and suddenly every Successor State was getting production lines up into full gear and issuing mechs like a common rifle...at least, that's how it felt to me.
I liked it best when mechwarriors wouldn't fight last man standing all the damn time (if you played campaign style where repairs cost money and parts were scarce), and would retreat from the field when they knew they'd lost.
I doubt I would have really gotten into Battletech if my first experience with it was after the Clan invasion.