Strangely enough, the community stayed fine after global release too. So we can't always blame everything on the Americans
The in-game messaging system is just enough to get by on. They added a "Sorry" option for when you stuff up too. It happens.
Some things don't necessarily mean what you think they would. If someone says "Leave it to me!" and runs off, it means they're going to wait by the portal while you all finish off whatever's left (it's both a safety and speed-up option).
There's a few others as well. Depends on context. Everyone usually congratulates each other at the end of a run, etc. But everyone is polite in actual chat as well (before raids and in guild chat. Even with non-English speakers, just saying "Hi" is common to say g'day before you start).
So try it out. It's one of the few games I can actually recommend putting some time into on mobile. It's always fun, but it's not a "time commitment" game. Play when you want, as much or as little as you want. You do get rewarded for playtime, but it's not a necessity to have a nice little 10 min jump-in once in a while, just to bash some dungeons. Remember that you will get raided, constantly and successfully. It doesn't mean you suck, it's just what you do in this game, even to friends sometimes
Think "Clash Royale" on quick-fun, with a better core-gameplay loop (two actually, dungeon raiding and dungeon creation, but dungeon raiding is the main loop), that doesn't pretend p2w means "competitive". Jump into a high level raid, or a low level one, whatever. Learning, gametime/RPG-levelling and skill gets you by, rather than "I bought 4000 packs of
competitiveness and am still in a lower bracket". There are no brackets here.
If you enter "level appropriate" rooms, you'll get your fair share of experience by killing stuff, which will level you up more quickly. Very quickly, until lvl 30-40 or so. If you enter "way higher than your level" rooms, you'll get bugger-all XP, because the higher level people (with better equipment), will be killing everything 10X quicker than you. But there's no wall between newbie and end-game content, because raiding content is all user-created, and anyone can jump into any room.
It's nice like that. You can scab gold and mana if you need to, but you're going nowhere character-level-wise if you do, unless you can actually help. There's times for both.
And when you do get destroyed by a low level group with a level 50+ destroyer along with them, don't worry too much about it. It's not actually predatory. They were probably just making sure that their guild could summon them and jumped into a room. Or they were randomly helping that group, and you probably lost considerably less trophies and resources due to them doing so. So yeah, you lost. But they didn't need your cash or trophies, they were just doing stuff. A lot of shit evens out in this game. Take it into context, and know how often the reverse happens to them. Enjoy your mana and gold from all the high-level raids you died in.
What goes around, comes around. Sometimes in ways you'll never know. As long as you're enjoying it, it's fine.
BANDAI NAMCO match-making "balance" might be exactly what the mobile platform needs. Like Dark Souls, but not as salty