Havnt read all the answers: Sorry.
It was more challenging in 2016. Today the challenge starts with Mushin Tower Floor 20 and some other Dungeons like Dreamtheater, Circle of Sundering is quite challenging solo content. Else the Challenge is the gearing and to fight the boredom while farming, because the time spend versus reward has some gap. I.e. evolving weapon takes about 140 sacred soulstones (plz beratter me if i mixed up the soulstones) for 20k peaches you get maybe 30. Depending how you farm these it takes about 2-5 hours. Farming these Items takes sometimes weeks. But i guess the Rewards are elsewhere within Clanactivities and Duels (which dont require much gear tbh). So if you decide to stay, find a clan that is supportive or invite some friends or so. If not, find another game. I think this has good mechanics compared and the difficulty depends alot on your class and ping.
hope this helps.