I can see that, but I think some better, more clever driving mechanics could have easily cleared up the issue. The Regalia should be better as far as player control. At least as an option. Having an open world game feels somewhat under whelming when you can't even adequately control one of the main adventuring/open world interfaces, I.E. the car. Now I'm not adventuring, I'm following along literally on rails again.
So here's the compromise. Make it able handle a little bit of off-road, but treat it like the luxury car it is. Hell, luxury "SUVs" aren't really SUVs. It can travel on paved roads, dirt roads, and some flat grass, but for the last two it has to go very slowly. Go too fast, and it get's really bumpy which damages the car, gets stuck, etc, etc. You have to get it towed back to Cindy for repairs. That's actually fairly realistic.
So you're left with using it for paved road/fast/long-distance travel the most, and using Chocobos for true off-road tasks like deserts, the woods, mountains, rivers, and any grassland that isn't perfectly flat. Also for local area travel.
Anyone who says that's too much detail to expect them to do needs to go back and look at the development cycle and budget for the game. They could have easily done it.