I feel like you are talking to me. My hi-ten Miyata commuter is a delight, purchased for $187. I changed the rims to Sun m13 (27"), Brooks saddle, new tape, powergrips on the original pedals, hondo front fender, bottle holder and rear rack and bags. Otherwise it's stock. I expect it to go for another 40 years. This winter I'm might spurge for a new chain, yo-ho!

I ride it occasionally along side my spouse, 30m weekend rides. It really needs nothing else. Rims did make a difference, primarily because I wanted to use high pressure tires. Feels much more sure-footed now.

Hi-ten bikes get a bad rap. Some ride like budda. Frankly, I get more fun and utility out of this bike than the CF Roubaix sitting next to it.