Excessive is knowingly denying someone necessary medical coverage solely for financial gain. If private insurers want to play that game then they can register as a non-profit organization or be an optional layer on top of a public backstop, such as medicare-for-all, an arrangement they've lobbied against for deacdes.
Sadly, they want to retain the ability to deny you coverage for any reason. Their maximum profit happens when they pay out as few claims as possible. The only reason they don't already operate that way is legal enforcement, so let's take that to it's logical conclusion
If you were in charge of denying or approving claims (millions of them), would you expect to make errors?
Would you expect every insured without sufficient medical knowledge to understand which denial was appropriate versus which was an error?
You know the answer, they would just steal money from people they don't like the pay for everything, and when that runs out almost immediately they'll implement rationing and waitlists. Tale as old as time.