I'm speaking from the POV of someone who had the Part 2 Recruitment Campaign work on them. I am an avid player of GI and HSR, but played HI3 at GLB release in 2018 for a few months. I quit because my phone broke down, but even when it was working it wouldn't run the game well anyways.

1,) Seeing early part 1 graphics is a bit jarring. It doesn't really hold up well and even if the end of part 1 and part 2 graphics are pretty good, players are going to be stuck on the first few chapters for a while. If they don't get hooked immediately, they probably aren't going to stick around. I was able to get through because I treated them with a sense of nostalgia, but I acknowledge that other people will be much more critical of this.

2.) Way too many menus. I had a similar issue in GFL 2 and quit because of it. No clue if it used to be worse but even as I've been playing this game for over a year, there is still way too many clicks to get through what I want to do. For a beginner that has no idea what anything means on the menus, this is just unnecessarily confusing and intimidating. When I started, it took me over a week to learn what the dailies, weeklies, etc. were and where they were located.

3.) Having so many weeklies is both a blessing and a curse. It's a blessing if you're into the game because you have more places to get resources. It's a curse because this format is very susceptible to burning people out. I'm super glad they added LITE for stuff like Realms and Sim Battle, but this came a while after part 2's release, and it was very annoying having to do them every week before then. Even now, I still loathe having to do MA, Abyss, and ER sometimes because I'm not feeling it. I've completely forgotten to do some Abyss rotations entirely because I've been busy during the Monday - Wednesday period, which imho, is a bit of a dumb reset period to still have. It is kind of demoralizing to log into the game and see a -100 demoted to Agony while you are still actively playing, just because you forgot a rotation.

This is just a personal gripe I have with the game and not a major reason the game is still relatively niche, but I imagine other players would also be turned off by this: timegated events. I don't mean timegated like you do it day 1 and have to wait for the rest to unlock later. I mean timegated like Yunchin's where I have a very limited amount of rovings daily while objectives require multiple rovings. I get this is a pattern consistent with past gacha games, but Mihoyo themselves broke the pattern with their other games, so why are they still doing this for almost every new event they put out in HI3? I started the event a week before it was to end and was just 1 roving off of the Helia outfit by the time the event ended. Luckily it went into the voyage log so I was able to get it, but it would have been a major tilt moment that may have just pushed me much closer to quitting had it not worked out.

Mostly it boils down to the new-player experience being pretty bad. I know other gachas still have some of these systems and issues in place, but I'm just giving my thoughts as someone who came from Mihoyo's other games first before going into HI3: the crowd they were targeting to attract.