How to measure achievement in a field where large collaborations are normal?
Years ago, I was on the college executive committee when we had to decide whether a certain experimental physicist should be promoted (to tenure, if I remember correctly). Her papers were of the sort you describe, huge collaborations that gave us no information about the extent and quality of her contribution to the project. But that information was provided, in considerable detail, by the letters from external reviewers. (Here "external" means outside our university.  In cases like this, the college waives its usual rule that so-and-so many letters must come from people who are not among the candidate's co-authors, because essentially everyone who has real information about the candidate's contribution is a co-author.)