[Kalimac]

It's true that the Mirkwood Elves seem more indolent and less noble than the others, but "The Hobbit" is altogether lighter in tone and also, if you remember, the Rivendell Elves don't really come off as paragons of solemn nobility in that book either (singing silly songs and ragging at the Dwarves about their beards, well, maybe it was a Saturday night party or something, but still it was pretty far away from the Rivendell of LOTR). If the Mirkwood Elves had appeared en masse in LOTR they likely would have seemed more solemn and noble, much like the Rivendell Elves, though probably tending a bit towards a "my way or the highway" view of things; they don't seem like the sort who would compromise easily.

Legolas seems quite intelligent but, like Muse said, a bit ignorant ("desperate" seems going a little far - after all he is very good at fighting, spying out land and sensing when something is wrong, and he seems to know a good bit of Elvish history). He doesn't seem to have left the Mirkwood part of the world before, but he may well have been to Dale and the Lonely Mountain - they weren't that far away - and mixed with people a bit there. He probably just didn't see the need to go anywhere else - with a Dwarvish kingdom, re-established town of Dale, big forest and the occasional pack of vicious spiders to occupy your time, you can go a while without being bored.