It's the persistent lie of the free market.

Yes, in theory if health insurance were a transparent, understandable product that you could easily switch with another one as an individual based on your needs and costs, market competition would optimize that product rapidly for service and cost.

But every single thing about that theory is wrong.

1. It's an intensely opaque process. You have no real way to know what the costs are going to be, what your needs will be, what your options will be. You can't even know what a doctor's appointment will cost under healthcare until you get the bill, sometimes a full year later (at least in my experience. Nothing about healthcare costs are understandable even to someone with an advanced medical degree. The layperson has no hope.

2. You also cannot easily switch it with another product. Open enrollment and contracts severely limit you. There's only fixed, stressful windows where you can change it -- and even then, you're back to point 1. What is the difference between the two plans in actual practice? It's all just gambling.

3. As you already observed, if your employer offers healthcare, you basically have no choice but to use that product because the subsidies are so intense. You are not an individual. The individual plans suck, are intensely expensive, and usually both across-the-board. The ONLY affordable option for the average person is the employer-offered product, so your choices are severely limited.

And it go this way because the most powerful agents in this system are not individuals.

With home/auto insurance, basically everything gets driven to a commodity product because all costs and risks are pretty uniform and predictable. That's why there is vanishingly little difference in the core products being offered by these kinds of insurance companies, and why the idea that switching your plan is sure to save you gobs of money is... improbable, outside of just periodic renegotiation of rates.

With health, the costs and risks are WILDLY unpredictable. The difference between an "expensive" customer and a cheap one is many, many orders of magnitude.

So naturally, risk must get hedged. The system's need for efficiency is going to try and package people together, just like any other high-risk, low-reward financial product. The need to group people is obvious, so we made it mandatory for employers to provide insurance as a weird workaround to the logical thing of government-run insurance. Now the customers are primarily employers who have TOTALLY different needs and desires from cheap, high-quality healthcare service. The free market will now do its work and optimize based on supply and demand. The efficiency gains will benefit the vendors (insurance companies) and the customers (employers). Individuals are not benefiting from market forces at all.

Free markets are great systems where they apply. They're really good for rapidly assembling efficient systems to get products to customers. But they only work where they work. The persistent lie of the free market is that EVERY problem can be solved with a free market. Nope. Only certain problems can. And where free markets don't work, that typically means you have need of government to step in instead.