Bitcoin and S&P 500

There's this notion amongst BTC investors that as the asset gets scarcer, the price would continue to climb. And this is a reasonable outcome for btc as there is fixed supply, and based on supply and demand, the price would skyrocket.

I have a similar question regarding, S&p 500. Let's say, S&P 500 gets a constant bid from investors all across and they keep allocating money on a monthly basis, while s&p 500 doesn't have a fixed supply a constant bid to buy s&p 500 would make it an up only asset isn't it? And could keep going up even if s&p 500 gets overvalued.

So if this is the case, wouldn't a good split between these 2 make the money grow with as less risk as possible?