Using TSLA, AMZN, MSFT, GOOGL, APPL as my makeshift 401k. In theory, what could go wrong?

I devout about 70% of my paycheck into 5 stocks, like the title says: $Tesla (TSLA.US)$ , $Amazon (AMZN.US)$ , $Microsoft (MSFT.US)$ , $Alphabet-A (GOOGL.US)$ , and $Apple (AAPL.US)$ .
Why does this feel like a both good and bad long term strategy of investing? On one side, I can’t see these stocks going anywhere, tech only will expand, and even if tech stocks crash, these stocks seem to be able to extend beyond just “tech”, ie TSLA with cars, AMZN with grocery stores, APPL with, well, phones and computers, Microsoft seemingly expanding to being a company that branches far past tech, and even Google even though operation as a search engine seems to have and will continue to cement themselves as a leading corporation in America.
Of course, I’m not saying anything special. I’m just wondering, is this a foolish plan? I know diversification is important, but it seems just dumping as much as I can in these stocks for the next 20 years is a solid investment strategy that should enable me to become financially free and eligible for retirement by 40.
It’s honestly nice not having to research new companies and hope my research pans out. Just dumping my money in these already established companies and believing that they’re going to be even bigger and more importantly still around and operating in profit in 20 years makes my investment strategy feel easy and relaxing. Yet, is it supposed to feel this easy?
Thoughts?