Bitcoin developers have many things in their consideration and to-do lists, not only scalability. Scalability means nothing if scaling up means less secured blockchain. So far, we have Bitcoin as a biggest and most secured blockchain to use, that's good and altcoin blockchains can not compare to Bitcoin blockchain in security.
I wish more people could see things this way. There's far too many myopic armchair pundits who can't conceive that it's a multi-faceted series of considerations and compromises. Easy gains are rare and few seem to recognise it.