The problem with high heat is it can crack the pan. This is more a problem with older 'vintage' pans than nowadays as the iron can have inclusions. What you want to be careful of is major temperature differentials, so for an older pan if it gets very hot, putting a cold steak on it, *crack*, has happened to me.
This is not to say that you can't use a cast iron pan at high heats, and a modern one, given the quality we have nowadays (no inclusions which are pockets of different iron composition in the pan) are less, just you have to let it warm gradually, and cool gradually.
Unless it is terribly pitted almost any cast iron can be reclaimed. If it comes down to it scrub it with a wire brush! My fave dutch oven was a garage sale find, and it looked like a piece of rust in a pan shape. I got in and scrubbed it with a wire brush and hot water, and a little oo grit sandpaper from time to time. Took me forever and a lot of elbow grease. And speaking of grease, greased it up with duck fat, baked it in the oven overnight. did that again, then did that again. Cooked with it for a week (where it sucked) put it in the self- clean on the oven, and started the same process. after about three cycles of cleaning, and seasoning, it got reasonable. Right now it is wonderful. You have to have some patience, and every time you use it, scrub it with hot water, dry it, and crisco the crap out of it (I like to use vegetable shortening, when you are first seasoning animal greases are the best, but for day to day, nothing like crisco, and you can slather it on thick if you are leaving it a couple days without using it, and it won't rancid on you).
Take it camping, slather it up with grease and bury it in the fire. Serious.
Anyway, once you start to use it regular like, you will get past the awkward phase, and it will adjust a bit to your preferences.
And nothing will really be a deal-breaker, do I occasionally clean mine with soap? Yup, and I cook tomato sauce in it too.
Of course, after eleven years of seasoning, I could probably hide from a nuclear bomb in my cast iron if I was a foot tall.
sourdough isn't a recipe, it is a process.