I don't think there's just 1 "crisis" people go through. I think there's a series of "puberty" type phases we go through: the 2-3 year old stage, the preteen/early teen stage, the getting out of school what the heck am I gonna do with my life quarter life crisis, the 30-something reevaluation stage (I went to a counselor and she said the percentage of clients that first come to her are overwhelmingly 35-ish), there's the dreaded 40-something that make men turn into total fruitcakes, and....it's like once a decade people start looking around and saying "Ok, what now?" It's not a bad thing to assess yourself, take stock, shed some dead weight, try new things.
As for being too young for crafts? Ummm??? Those things are NORMAL crafts once people have little kids, so you're normal. You found something you like and are sticking to. So what? And YES as someone else mentioned, they are coming back "in"--a lot of my friends have started reading books like "How to sew a button (and other nifty things your grandmother knew)". I do think that physical exercise could do wonders for your mood and how you feel about yourself. Just something about getting out in some fresh air and sun for a swim or brisk walk, even a bike ride (it doesn't have to be miles and miles like some people, just get moving) will help you feel more energized. I thought it was weird that expelling energy makes you feel MORE energy, but it's TRUE. In the meantime, I totally think you should check out some clubs in your area. The community I lived in before had bunco, bridge, sewing, and quilting clubs (also Spanish, Russian, Mandarin, cooking, breakfast, active seniors, small business networking, art, several neighborhood sports teams like softball, flag football, swim, indoor soccer and a playdate network). I'm sure every community has a club for bridge and quilting! Perhaps socializing with people who share your hobbies would be more fun. I know they're out there, or there wouldn't be clubs for them! Also, I was at a ladies Bible study for a few years where 3 out of 15 women were avid quilters, 2 did basket weaving, 10 of them at least knew HOW to sew, whether they did it often or not. A couple were beautiful bakers, a couple (myself included) were great cooks and really enjoyed that. Half were into canning (which is also becoming popular again).
I have a few friends that have gotten into crocheting, knitting, sewing, and quilting. (Me, I really seriously don't know how to sew a button, and that is not an exaggeration....but it has started becoming the "in" thing to do). Seems like social fads also go through phases: EVERYONE my grandma's age knew these things; it is how they actively supported the family, then people my mom's age rebelled and wouldn't learn them, focusing more on being "free" of the "Leave it to Beaver" stuff and going to work to actively support the family. Now the people my age are a bit in the middle, trying to figure out what works for us. But I think it's perfectly fine to follow your bliss, whatever you find interesting, stimulating, and satisfying. I like to make scrapbooks and photo books. I'm not hardcore or anything (I don't have time to be hardcore at anything because my boys are very young), but I enjoy it. I'll swing by Michaels to one of the free classes every once in awhile and there are ALWAYS women of all ages there.
And if you think you're actually in a slump: it's probably that you ARE entering a new phase (you mentioned the kids leaving the nest, and that's a good thing, but that IS a new phase even if you're happy about it). Write out a little bucket list, lol. I'm 35 and I made one at 16, and revised it at 30. You could even do a mid-year resolutions list or something. Then just start doing a little every day towards seeing that list come to fruition. That could be anything from becoming an expert in one of your hobbies, or submitting one of your projects to a contest or charity, or even making a little money from it, or pursuing a new goal. It could be anything! Just give it a think, do a little research, and start moving towards it.