It's actually the other way around on many.. In many ways they are becoming less complicated and easier to work on. The car I had before the 05 Corolla was a 89 Honda Accord. It was actually smaller than the Corolla. Sat a lot lower and had a 2.0 L vs the 1.8 L. But it got probably 8-10 less mpg than the Corolla. I averaged about 27 mpg with a city/highway mix. The 89 Accord was more complicated than the 05 Corolla. It had a feedback carb, and about 129 vacuum lines. :/ Working on that car was like going in for a root canal. Access was hard to almost anything. Just changing the starter was a PIA.. Hardly any room, so when you unbolted it, you then had to snake it through pipes to the other side to get it out. It was a good car, but I hated working on that thing. :(
In comparison, the 05 Corolla should be a relative breeze to work on. Under the hood is much less cluttered, few vacuum lines, no plug wires, distributor ,etc.. No goofy feedback carb. The Honda had a timing belt which needed to be regularly changed. The newer Corolla has a timing chain which does not require regular service. I've never had to work on it yet because so far nothing has broke, but from looking at them, I'd rather work on the newer Corolla any day. I'll also take it's 8-10 mpg mileage increase. It's coming up on 60k miles, so I'll probably give it a good going over, and likely should change the serpentine belt on it just to avoid future problems. If I do, that will be the first time I'd actually had to do any real work on it besides changing the oil.
******** I agree... OBD II vehicles are much easier to diagnose and repair and tend to be much more reliable than the older cars with feedback carburetors & miles of vacuum lines.