Nobody's going to vibecode an internal salesforce. On the other hand, the barrier for ex-salesforce engineers to take their knowledge and build a competitor with the 20% of the features that represent 80% of the usage is dramatically lower.
I think the SaaS landscape will look vastly different in five years.
Your engineering focus is exactly the problem! Salesforce as software is a piece of crap, no one is arguing that. But companies continue to buy it because (a) it's familiar to all their sales & marketing people, (b) SFDC is all set up to be able to sell into other large companies (not a trivial task), (c) it already does all the legal, regulatory and compliance stuff, worldwide, which is hugely complex and boring to replicate and needs people on the ground in multiple countries to achieve. Coding is not the problem here.