I'm a junior and I probably spend a similar amount of time thinking vs reviewing. I rarely write code unless it's about <5 lines.

I find the instantaneous thinking easier now. I can have several ideas in mind, and have a concrete implementation made for each, making it easier to compare alternatives. Although, since each problem is alone easier to think about, I do end up handling a greater number of problems. But I expect that my total volume of thinking is likely the same as before.

Where I do certainly feel more tired is when I try to solve too many problems in parallel. If I try to do that, I end up constently dropping context. So I generally try to finish a big chunk of something before switching (usually that means getting it ready for another code-review cycle).

I do miss writing code myself. It's certainly satisfying. It's just significantly slower in most cases. I try to do it in my free time.