First of all I'd argue that the game loses something for not having this feature. One of the best parts of PSO2 is how driven it is by geek culture. We have several crossover designs and characters, from Vocaloid to Persona to the plethora of anime injected into the game. Taking away symbol art removes a lot of the expression via memes, and cultural reference that has breathed so much life into the game, and offers a social experience far more grand than any other MMO/Looter game. From WoW to GW2 to FFXIV to BDO; there is no competition to the level of social interaction and how well this game facilitates it; and symbol arts are a part of that. Name one other MMO/Looter/RPG that allows for someone to get smacked down by a boss, where you can literally respond with a surprised pika face, a popular meme broadcast to everyone to display your shock in how you ended up in that situation, regardless of vet or newcomer. This is something special about PSO2+NGS and it should be preserved.
Toxicity alone isn't a valid reason. Anyone can be "toxic" with anything; including simple auto chats. An "op in" function was reasonable to allow the more sensitive people to not have to partake or see anything they view as offensive, while also protecting streamers; but that standard shouldn't have to apply to everyone who can handle it and is not easily offended. There is no reason to detract from everyone else because some people don't like it and a few people abuse it.
Bots are not a valid reason either. What happened the moment these came off? We were back to how it was in PSO2 Classic, Bots would just spam in text, and maybe that makes it easier to ban them; but it makes no difference to the player experience. If bots hide in some corner in central city we still have to hunt them down and block them. Also the far more effective measure was the Aina quest thing. This should have been implemented first before killing a system, that ultimately punishes players and detracts from the game because of bots.
Sexual content is slightly valid. First off this only really applies to full nudity, as the game is very sexual in nature, and even emphasizes partial nudity in it's ESRB rating. Where full nudity becomes a problem is the ToS, and breaking it. However, we have a simple solution to that: Reports and bans. --However, I'd argue this isn't completely necessary either. We have a game rated M; and like all online games the expected caveat is that the "Game Experience May Change During Online Play". By analogy just like the people who are able to by bass the censor to make some racist or other offensive joke, or the couple who are ERPing in their personal quarters, and of course those who post fully nude symbol arts; have effectively changed the experience. But this is something adults (M rating remember) should be able to take in stride and easily move on from. People who do not appreciate, wish to condone, or wish to participate can easily block those people on their end. More over; If you are a minor the game doesn't even allow you and others to communicate and we effectively protect them from being exposed. But that is ultimately irrelevant; If they do not want this content simple reports and bans are all you need.
Symbol arts can be degenerate, Anime as a whole can be degenerate as well. But this is the community we have, this is part of anime geek culture, and Sega is complicit for most of the degeneracy; Just look at the emotes like banana boat and the various outfits we get, even their own PSO2 Comi is on par. Plus see how the Japanese version is run. We pretend like global is such a stark difference in attitude and values, but honestly with the exception of playable content; the vast majority of people who enjoy this game will by extension share the same values as any JP player, otherwise most of us wouldn't even play this game. We'd go to FFXIV or WoW or BDO or GW2 or Destiny or Warframe, or wait for a new MMO or looter game. Frankly the people who don't share those values can easily block out the things they don't want to be exposed to, and considering how tiny yet vocal that minority is they could easily move on without looking back, and financially sega; you wouldn't even notice.
Ultimately SA is something special to this game, and gives it such a depth of life that other games do not, it along with a few other systems facilitates social interaction that other games are lacking; and ultimately PSO2 is lesser without it. Like literally anything it can be abused; but that isn't a reason to punish everyone else's freedoms because a few bad apples upset a few other bad apples.