That's great that it worked for you and your family but that does not work for all kids. My oldest has SPD, probably eats healthier than most people as he prefers raw veggies to just about anything, but they don't have a lot of calories. We are always on the edge of intervention for his weight, so for him, we do have to cater to his particular and very picky tastes (no sauces or gravies, nothing mixed together, the few proteins he will eat). We can't restrict access to foods he will eat because in addition to being picky, he doesn't eat much at a time. We are thrilled whenever he eats anything. I once watched my youngest trying to show him the pulled pork he had in his bowl, trying to offer him some, and him running away gagging and crying like he was being tortured from the smell alone. So, no, that is not a solution for everyone. The picky eater question is very valid.
Pickiness also isn't necessarily the result of parenting. My youngest will eat and try just about anything set in front of him. He can identify pesto and other things by taste. We didn't raise him any differently than the oldest. I think many picky eaters have mild forms of SPD and no amount of tough love will change them.
OP - we have never done Biergarten as my picky eater probably wouldn't fare well there. Sounds like Mac & Cheese will help you out there (mine will only eat Kraft, the way his dad makes it). We are trying Teppan Edo though because steak is surprisingly on the approved list for him. I have found the menus at All Ears to be very helpful. Especially when is comes to QS. I typed up a list to carry of QS locations that have items he will eat so that we can run get him something from nearby if the QS place we stop at doesn't have anything on the menu he likes.