That's been the biggest problem I've had with Plurk so far, too- it's hard to tell if I can't find people or there just aren't really people. I think the userbase is primarily Taiwanese, but beyond that, I've been keyword searching here and also looking at likes of posts / fans and friends of other people who post things I like.
n0495456: yeah its super rough (ruff) like sure half my tl on twit isnt my language either but like i love artists from all over but its so @.@ trying to find people. kinda struggle the same on masto like is no one there or am i bad at this. but plurk (and my masto instance) are one of the few that i was satisfied with their nsfw rules (ಥuಥ)
In Plurk, some long-time users tend to prefer privacy, and their friend circles are already established, making them less responsive to new users unless they know each other more. Additionally, with the increase of bot accounts, some users have become more cautious.
However, if someone is looking for deep interactions or enjoys sharing without worrying about others' responses and wants to post whispers visible to people who search specific tags, Plurk is a great platform to cultivate that.