The government would still need employees to basically do everything that the people at insurance companies do. Theoretically it could be more efficient, realistically it would not.

The real problem with our system is that for anyone who is going to hit their deductible, or especially their out of pocket max, the costs no longer matter at all. Sure, that cancer drug can be $500,000. GLP1 drugs for $1,000 a month? Why not?

Of course, there's no free lunch on this. In a single payer system you get things like the UK not approving certain cancer treatments for people over a certain age, certain medications just aren't available, etc.

Otherwise you could make every plan a very high deductible plan, possible just not cover medications at all, etc. But then people will complain about people not being able to afford things, especially in the short term.