I know you didn't ask for suggestions, but here's mine: the one thing I care about a CRM doing really well is pipeline / funnel management, i.e, the ability to define a set of stages that a contact goes through to close a deal or reach some other desired result and track contacts as they move through the pipeline(s).

For example: unqualified lead -> qualified lead -> responded to email -> discussion with sales rep -> made purchase

Being able to organize my contacts in this way and quickly see which contacts are at which stages and easily move them between stages (ideally with an API endpoint) is a super powerful way to drive day to day workflow (and automations like follow up emails, assuming there's an API endpoint for querying).