Welcome to bikeforums! You are doing everything right if speed is not your prime concern. Smooth street tires make for faster, easier riding. Sitting upright is better for traffic awareness, and wider, 26" wheels and tires tend to be more resilient than thinner 700 wheels. My main commuter is a more of a touring bike with a longer wheelbase, and fatter tires (although 700s). But for over 15 years I commuted exclusively on a MTB-based commuter. It is now my back-up commuter/utility bike and with studded snow tires my winter bike.

What I did was to add taller (higher) gearing to my MTB commuter to get higher cruising speeds. I've never ridden any distance with a suspension fork, but it seems most people here recommend locking it out for commuting.

Sturdy, comfortable, capable...MTB based commuters are a very good way to go.