What do you get for the 90 bucks again? I don't really think it's likely to be worth that
There are bounties for playing through certain story missions each day, that make some worth revisiting at any level at a given time. You can also all play Crucible (PvP) together if you're into that (edit: ah, oh well). Generally speaking though, it's not common to redo old Story missions at low levels, though I'm sure you could find people here to help if you get stuck. You'll have to get within their basic level range to do most of the interesting content. For the most part though, the more relevant point is that getting to ~26 is quite quick, relatively. The gear you can buy from vendors now will get you further than the gear you could buy from them at launch. You're definitely not "hopelessly left behind" or anything like that.