Why is phishing still the main way in?
Because it does not target the machine but the person in a hurry. A fake email from a supplier changing its bank details, a fake message from the director asking for an urgent transfer, a fake delivery notification: no anti-virus blocks a deliberate action taken by the user, with their own credentials, on a site that looks like the real one.
It is also the cheapest door to close. Where bringing an estate back up to standard needs a budget and a timetable, awareness produces a measurable effect within a few weeks — and it benefits every other protection, since it cuts the number of incidents to deal with.