The US stock market has never not gone up long-term...

I am fully invested because it would be an absolute self-mog to not be invested...but is it really going to keep exponentially going up into infinity barring and extreme event? I feel like we may be going the way of Japan where it stagnates for 20+ years at some point...then where will we find returns?? Real estate? Accept that we missed possibly the greatest inflation of wealth of all-time because in our generation we were unfortunate enough to have a mass stagnation?