No because the shares (in theory) have value behind them.
So does property.
If they went up overnight, it was because the value of the company changed not because the purchasing power of money changed.
House prices go up because the value goes up too. The value is the neighbourhood, the schools in the area, proximity to public transport or shopping etc. Shops could be built someplace and the value might go up. A highway could be built nearby and the value would go down.
Here’s another question though. That old lady/man everyone knows of that owns dozens or hundreds of houses, do you think they ever sold any? They can still accumulate wealth without paying tax by simply hoarding it like a dragon.
That would be tackled with a wealth tax not a capital gains tax. I do think an argument could be made for a wealth tax for sure.
But if I had my way I would scrap all those taxes and replace with a financial transaction tax. This would be simply done by adopting a digital currency and taking a tiny cut on every transaction automatically. No muss, no fuss, no IRD, no nothing. Just a premined currency that the government controls the supply of.