[eitally]

I think the important thing to put on the table when having career & performance conversations with team members is to acknowledge that career progression via deep specialization is a perfectly valid path -- or that it isn't. This is often a business decision, and frequently the business is ok with just mediocre or competent SMEs, which will frustrate folks who want more, but at least you'll have created the "radical candor" you need to talk about it.