Nobody here, or in real life, is a gifted stockpicker who will pick the 4% of stocks that contribute to most if the stock market returns.

This number presumably comes from the much-quoted but never-understood recent study.
Though you're right that it's unlikely that any given person is likely to pick one of the few very big long run winners, owning one of those stocks is by no means necessary in order to do very well.

The reason is simple:
Most stocks make a profit most years, so it is dead easy to do well over time even without the luck of picking a few outstanding long run winners.
The chances of a random US stock having a positive real total return in a one year period since 1960 is 56.5%.
This is pretty far from the 4% in the study that got so much press, and a much more useful and meaningful number.

Consequently a diversified portfolio of randomly selected stocks which is reconstituted from time to time almost always does just fine even without the few long run superstars.
In fact your chances of beating the S&P 500 this way over the long run are remarkably high, not low.

One thing worth mentioning is diversification within your fixed income. ST and LT, in ST include a few floating rate ETFs like TFLO and FLOT.

I think another thing worth mentioning is never to buy a bond or bond fund with a negative prospective real return.
Which is almost all of them in the recent era.
There is no reason to take on return-free risk. Disregard out-of-date advice that hasn't adjusted to the times.

To be fair, at least the real yield on TIPS ladders is positive now.
You can build a 20 year one which generates constant real income (in CPI-adjusted US dollars, anyway) with IRR of 1.86%.
Current cost $16.66 for each annual real $1 in annual income for 20 years, if this calculator is to be believed
https://www.tipsladder.com/
Not an attractive investment return compared to what you get in equities, but it certainly wouldn't cause sleepless nights. Unlike most bond funds.

Jim