Collective bargaining comes with a lot of benefits - doing it at the employer level is just extremely unfortunate for jobless persons.
There’s tons of near zero cost investment options from Vanguard/Schwab/Fidelity, you can go to healthcare.gov for health insurance, and you can go to term4sale for life insurance, etc, etc.
The only difference nowadays is that employers large enough to do non discrimination testing and handle the paperwork have an unfair advantage over small business and individuals by being able to compensate people with tax free benefits, whereas small business and individuals can’t.
When shopping for individual insurance you're trying to balance a lot of future unknowns - will you puncture your kidney in the next year and need dialysis? How likely is it and how much is 50% POC (Price of Charge) coverage worth to you? Are you going to need an oncological drug due to a sudden cancer diagnosis - those can easily run into the hundreds of thousands of dollars a month - I hope you don't accidentally choose an insurance that covers treatment for all variants of cancer except the one you need treated.
The health insurance market is insanely opaque and most employers pick a reasonable plan and, when that plan inevitably refuses to cover a necessary procedure for their employee - they bitch and moan at the company over the phone and leverage their collective bargaining. There are also some really good reasons that the ACA didn't extend the individual market as a replacement for medicare since those insanely expensive and obscure treatments get more likely as you age.
Right now we're sorta surviving on insurance supplemented by go-fund-me and good will but that's a terrible system. Sudden insane health expenses can happen to you - I hope they don't, I wish they didn't happen to anyone - but our current system treats most folks decently well and really screws over a select few, and not due to any particularly stupid decisions on their part in most cases.
I think the biggest problems with employer-provided benefits come at the 'employment transients' (i.e. the time just after leaving jobs and while getting new ones).
HR people can only get numbers from a small number of insurers after an excessive amount of time and have leverage as weak as someone buying a new car.
If the precise definition of the product is dictated by the government then what differentiation are the insurers actually providing that adds value to the equation. Right now insurers actually do do a fair amount of good work trying to assess treatment efficacy and ensure that their customers get the best outcomes within a reasonable budget. If coverage is standardized then they're just acting as a pool of money - cash goes in, it comes out, occasionally one of the pools will go bankrupt and catastrophe will befall a lot of folks - or else the government will step in and save it so... why not just let the government run it?
Insurer's roles would be marginalized to competing on doing just enough administration and estimating/negotiating cost/pricing.. They also would still have incentives to cut costs as they get temporary benefits of cost cutting until copied by the other insurers. It's not a lot but it is areas medicare has problems with (and pricing would get harder still without a reference private market) and retaining a private layer is more compatible with the politics of the US even when it is a pure cost.