Economical commuter, with a tolerable slushbox?

You may be thinking about significantly older cars. More modern auto transmissions are much better. A car from the mid-2000s won’t have the same problems you mention. When you test drive a candidate, take it onto the highway and see how it works. There is a long, steep hill near me that I use to test any car I want to buy. If it can’t make it up the hill without downshifting, it’s off the list. Set up your own “obstacle course” to test candidates on.