wrt the hypothetical of "should the glue-working engineer get promoted to senior engineer on par with the engineers writing code?" i actually come down mmmostly on the side of "no", though context is key. here's my reasoning.
until someone can work autonomously && use good judgment, they should not be doing glue.
partly it's because tbh good engineering judgment is needed *even more* for glue work, it's just not as obvious.
also? glue is expensive. if there's a TON of glue work to be done, some managers and tech leads are not doing their fucking job.
senior engineers should absolutely be recognized and promoted on the strength of their full contributions to the org, including all the super valuable glue (or better yet glue-elimination) work that they do to keep things humming. and yes, promoted too.