That's simply not correct.
And important note here is that I'm obviously not advocating for investing 1 million dollars in a single SP500 ETF. For some people that may very well be the right thing, but if all you've got is 1 million dollars, you're taking a ridiculous risk putting it all into one thing, because what happens if some years down the line, stuff happens in your life, and you need to take out a good chunk of cash and it coincides with a terrible market, not a stellar combo.
So obviously basic diversification is critical, based on your personal situation. Can be accomplished easily with 3-5 cheap ETF's. Buy and hold for many years, until your life changes.
But as for SP500.. You could have invested in virtually any SP500 high, and as long as you can hang on for more than 10 years, you can almost not lose. Quite the opposite, sitting in cash is sure death, because you're gonna miss all the highs, sure the market may drop 30%, but that dip could have been in a period of 40% gain.. And you're losing out on the most essential part of making money long term: compounding interest. So.. Just invest, there's (almost) no bad time.
As for OP and timing.. I wouldn't know.. Way too many unknowns to give any kind of specific advice.
Someone else linked to the "three fund portfolio" and that's close to what most people should do. Get VTI, VXUS and BND in some ratio based on your age, personal situation, investment horizon etc, and then just let it sit.
Spoiler: time in market beats timing the market, historycally.
To OP: Get a financial advisor ASAP, $1m is enough to justify it. You also have a lot of tax implications that you probably haven't thought of, a lot of work goes into avoiding taxes at those stakes.
edit: See https://www.bogleheads.org/wiki/Three-fund_portfolio for an example of a simple, well diversified three ETF portfolio.
To repeat, this is NOT a comment about ETFs; it's only about where the word "foolish" goes.
Honestly this whole thread is a dumpster fire I'm leaving this one alone.
https://www.marketwatch.com/story/why-way-fewer-actively-man...
A vast majority of advisors (90%) aren't going to beat an index fund. You are just giving money away money by hiring an advisors.
Unless you want to pull offshore tax shelters or Real estate depreciation schemes its not super complicated to do taxes. Invest long-term and you are getting capital gains tax.