MMO is used as-is in Chinese gaming chat. Standard members of the genre referenced in Chinese:
魔兽世界 (World of Warcraft),
剑网三 (Jian Wang 3 / JX3),
最终幻想14 (FFXIV),
逆水寒 (Justice Online),
原神 (Genshin Impact, sometimes loosely called MMO though technically not).
太肝 ('too liver-burning') is the standard complaint about MMO time investment.