I don't think any car with well over 100,000 miles is highly likely to be reliable. A high-mileage Toyota will be more reliable than a high-mileage something else, but the miles still take their toll.
The hard part with buying anything right now is that prices are very high, even crazy high. Maybe you can find someone with a car you like willing to trade for the Highlander, if you'll be getting rid of it.
For fuel economy you're going to want a four-cylinder engine or a Hybird. A Camry seems a better bet than an Avalon, but $10k for one with reasonable miles right now could be tough. Same for a Honda Accord. A quick search finds that even a 2014 Mazda6 with mileage in the low 100s might be barely possible for $10,000 right now. With a Prius, which might not deliver the comfort you'd like but which will be reliable and efficient, you'll be looking at a 2012 or older.
Is your commuting stop-and-go, or cruising on the highway without much traffic? If the former, a hybrid might be a good idea. Otherwise, just an efficient conventional engine.