I think Tony Isaac's point is a company that is already very big cannot get a lot bigger without getting smaller first.
Intel is a good example of that. Its stock-price had a big rise up to mid-2000 until the dot-com bubble burst. Then it fell by a factor of two. For about a decade and a half it did pretty much nothing, then rose to challenge its 2000 high starting in early 2020. Then it fell again, reaching early-2010s levels last year. And then suddenly it had a spike upwards in the past year or so, fed by new management, the AI surge, and partnerships.
In all of these cases, Intel's stock price rose after lows, some of them significant. It didn't just keep rising, because it couldn't. There's only so much capital in their sector of the marketplace. An already-large company would need a whole lot more of that capital to grow, percentage-wise, than a smaller company.
You are right that individual investors are not limited by market-cap. However, individual investors need to consider how much more a company's stock-price can grow if it has already grown a great deal. It may need to sell off before it can rise again.