In Hunter x hunter many fights would go on for even dozens of episodes and the ant arc went on for a very long time as a result

Most fights were done in an episode or two, the show would have series of fights that may go on for multiple episodes, but most individual fights didn't drag on too long. Besides, how long the ant arc was is usually people's #1 problem with the show. It doesn't get excused and is usually criticized.

Nowadays an action or shounen anime would be criticized to the ground if a fight even takes up one episode

Nice hyperbole. 2-3 episode fights still do very well andncan be hype as fuck. The problems arise with bad pacing and dragging on fights for no reason (or filling them with speeches and monologue), not long fights.Also depends on the length of the series, a 12 episode series can't have many long fights without running out of airtime, while. 50+ episode series can do it more comfortablely.

Sure you could argue that the writing makes up for it but does that instantly excuse it?

Haven't seen Berserk but things are usually "edgy" because they aren't explained and are just blood and gore for the sake of it. Good writing means it's not edgy no? Besides, edgy is thrown around a lot and pretty much just a buzz word now.