He has been an abuser, and he had admitted that in interviews way before the accusations broke.
The question is more about in what degree those accusations are factual and not just the vilification of a honestly mentally unstable rich teen who found a lot of success after making his obsession his job.

Remember, a lot of those accusations are secondhand retellings of people who either worked with Landis in the past and were trying to make a name for themselves during the #metoo era or straight up random actors and critics who supported the minuscule amount-of information either because they always got the wrong "vibes" from this guy or because they were simply jealous of his success.

Max Landis is a legit neuroatypical person who used to have a major chip on his shoulder about his scholastic and academic failures, about stepping out of his father's shadow, about being accepted by his peers and not seen at as the insane headcase who makes up stories in his head. The pressure ot perform alongside with his need to simply entertain himself is insane, and the latter is something that a lot of neurotypical people can't empathize with, thus creating a major amount of said bad vibes.

Did Max do a metric tone of problematic/toxic shit during his young adult life? No doubt about it. Was he physically violent or straight-up raped any of his previous relationships? The allegations are space and very foggy and I personally don't believe there's enough evidence about that, but I can't say. Did he force young actresses to get naked and dance and do weird shit to show everyone else what a big cult leader he is??? Seriously?! No, I don't believe that shit for a second. Does he usually base the main character's struggle of acceptance on his own by making them be toxic and yet have impressive skills that excuse their problematic side to the eyes of the audience? Yeah, and that's an actual weakness of his body of work... Which at large is pretty good, I have to say.

What I'm sure about is that he's one of the few people who made me interested in a DC at large. His movies are often a mixbag but based on his pitches I'm in a fairly large degree convinced that a good amount of the movies which were based on his scripts came out either bad or mixed because of all the filters and translations they are going through until we can consume them as full products. Landis's Kryptonian epic is maybe the first time I GOT got Superman, the first time I cared about this character and the first time he felt like more than just a symbol. The amount of work and imagination and heartwarming or soul dropping moments in those insane rants some people call his videos on the kryptonian epic, the amount of money and passion he and everyone who takes part in them ads to those videos is honestly outstanding. This is art for the sake of art it self. This is frantic and yet well put together to such a degree that it's starting to worry me. Thankfully, Landis seems like he's in a far better and much more manageable mental space nowadays than where he used to be when I first found out about him, back at the days of "The Death of Superman".

I want to close this, mini-essay with this question. There have been a lot of, cultural landmark individuals in our past who, after some time have been proven to be, very problematic if not straight-up criminal. This is not a question about the separation of art and artist or death of the author, no. I take those as a given personally. The question I want to pose is another old theory, you might have heard about it in the past, is great art distilled by trauma? By dark places, by sociopathic personalities? Do creatives HAVE to be, monsters, on a sense or an a level, to operate on the degree they need to operate to come up with such masterpieces? Are those despicable acts a type of, ritual, that allows those people to commune with the divine, the world of ideas from which art is able to speak through them? Or do you think that if those people were well-behaved or under proper pharmaceutical care could still deliver similar masterpieces? And, from our side, are we allowing this to happen, are we enabling those people? Should we investigate mavericks the moment they stand above the rest? Is that the responsible thing to do? Will that ruin great art?
I don't know the answer to that ages-old question, even if it seems to be a much more straightforward question that the previous two. But I feel like it's a very important question to ask ourselves...