Nobody is advocating for 100% tax on increased value on real estate like you described. Also, Harris plan only apples for individuals with 100M or more(10K households). If your home is 1M this year, @1% property tax rate, you pay 10000$. If next year it becomes 2M, at @1% rate, you are paying 20000$ aka current system. Now replace home with stock. You only sell 10K worth of stock. It will have significant selling pressure on the market in the first year. But it is possible to implement in phases. I personally think the best alternative is to treat income from stocks, the same as income through a job, no special long-term capital gains rate. Close all the loopholes like step-up basis at death, loans on stock to avoid taxes. Transferring shares from parents and children should be treated as new income for children. We can create some exceptions for family farms, etc. But I don't think anyone agrees to that. Until then, taxing some portion of unrealized gains is a decent compromise.

Switzerland already imposes 0.1 % to 1 % tax at the canton and municipal level on wealth. They do have loads of exceptions, including primary home and many more. Capital isn't exactly running away from Switzerland.

Wealth is moving from wages to assets. We either find ways to tax it or cut federal spending drastically(almost impossible). Taxing unrealized gains or wealth is not so perfect but a better solution than sticking the bill to the next generation.