Your impression would be more or less correct.
Do I still get to say I'm new? I'm going to say I am anyway just because I'm part of the fairly recent wave of recruits rather than the rest of these guys who've been around for years. From the perspective of a new(ish) person, I'd say this group seems held together more by the forums than in-game activity, which I like. We may not always have time to log onto STO or TOR & run something, but we can always hop on the forums for five minutes to make a post & still be an active part of the group. I wouldn't say RPing is mandatory, however. I've been slacking on doing it myself due to a severe case of writer's block, and no one's even said a word about it to me.
If you're dead set against RP, you won't enjoy this fleet as much as you could, but in the end whether or not you enjoy the company of the fleet's members & activities is probably more important.