I am another "retread," who returned to riding after a long hiatus.
I bought a copy of the bike I'd last owned, a 1982 Yamaha 550 Seca. I felt immediately at home on this bike. It was inexpensive, had been well maintained, and I had absolutely no problems with it (well, none I couldn't fix easily) over the two years I rode it. It got me back in the saddle and let me rebuild my skills, on a bike that was familiar and easy to ride. And when I did sell it, I got more money than I'd paid...
The only reason I decided to upgrade to a new bike was because I wanted modern tires and suspension. I attended a lot of demos, and rode a lot of bikes, during my two years on the Yamaha, and that definitely helped me decide on the bike I wanted. I won't buy a bike I haven't ridden--ya gotta know what it feels like in motion. BTW, I'm still riding my "modern" bike 5 years later, and loving it.
So, that's what worked for me. I don't know why you don't want to buy a bike from the 90s (or earlier) to get you back on two wheels--just like a newbie rider, it helps to have a bike that is unintimidating and cheap to start on, and they're generally quite reliable. Then, once you're back in the groove, get your butt onto some different bikes, to see what the modern bikes feel like.
