I never botted or was even into that scene in diablo 2, so I am legitimately curious about this: could the bots run through the hardest content in the game, or were the bots unable to handle anything serious and merely used to run through easier content that would be trivial for the given character?
A well equipped Hammerdin bot could solo Hell Baal/minions with minimal risk very efficiently, which is the final act boss. In fact many people leveled in the 90s by following bot-made Baal games.
However most bots ran bosses like Pindleskin and Mephisto due to ease of access = faster runs and there wasn't a need for great equipment on the bot unlike a baal bot. and there were only a few unimportant drops you were missing out on that only Baal could drop anyway, iirc.
However the hardest content in the game was Uber-Tristram, which I don't think could be botted. It could be solo'd with certain builds/godly gear (i.e. duped runeword items), or you needed a good team. The reward being there was the Hellfire Torch, a charm with godly bonuses, but to run the Uber-Tristram you had to collect a bunch of mini-keys/artifacts first which was time consuming, so there were bot runs to collect these because they dropped from set bosses in each act (countess, summoner, and Nihlathak).