Do stocks rise simply because more people have the opportunity to invest?

It sounds like a completely banal or stupid question, but I have the feeling that simply investing through Neobrokers means that a lot more stock volume is traded. Compared to 10/20 years ago, surely there are so many more people in ETFs that this is already having a noticeable effect? Can you even compare today's share prices or key figures with those of 20/30 years ago? Is this a water is wet hypothesis or does the idea make sense? submitted by /u/JonSnowKnowsNothing9