I started commuting on a "ten-speed" that I had for some decades and that was the only kind of bike I could get at the time I first got it. When I replaced it, I tried the upright hybrid and the semi-bent-over mountain bike. The upright, in contrast to the road-bike style, felt too upright, so I went with the mountain bike. After some years of that, I found it too bent-over for my liking and replace the stem and handlebars for a more upright position. The point being, I think that the hybrid felt too upright only because I had been too used to the road bike. And, thinking back to 40 years ago, I remember that I never liked the road bike style anyway, it just was all I could get and I eventually got used to it. So to restate what was said by others, try lots of bikes.

It is possible that after a certain age, the riding position of the road and mountain bikes, where one is bent over and then has to tilt the head back to see where one is going, is hard on a person. I was down for two months last year while a chiropractor fixed up my back, neck, and left arm. Right after that is when I got my new upright riding position. I go only 12 miles round-trip.

It seems that many of the mountain bike styles do NOT have attachment points for front fenders. Watch for that. I personally think fenders are essential.