If you can “only win 40% of the time” then all the people sitting on trading floors earning 7 figure salaries and bonuses (even if they’re almost all virtual trading-floors, these days) must be doing something terribly wrong, because they seem to believe the exact opposite!! 
This myth just won’t die out.
At least, in forums full of struggling retail traders it won’t die out.
And it gets continually reinforced on Youtube, in PDF’s and on websites where people are selling stuff to ill-informed audiences of struggling traders who all believe that (because it’s what they all tell each other all the time, regardless of it being totally wrong).
In other places, where people are actually making a living from their trading, in circles frequented by successful traders, in the world of professional trading, it didn’t have to “die out” because nobody ever believed it to start with.
There’s a kind of beginners’ myth that you need a high reward to risk ratio (and can therefore only have a fairly low win rate) to do well.
In Babypips (and at one other trading forum) there’s a kind of nearly universal assumption that win rates “shouldn’t” be too high, because distances from the entry to the stop loss “have to be” quite a bit bigger than distances from the entry to the stop loss.
It’s complete nonsense.
But heaven forbid that anyone should ever try to have a high win rate and a lower “R”.
They might be hounded out of the forum!
In professional trading circles, of course, there’s more or less the opposite assumption: that stop-losses are wider than targets, and win rates high-to-very-high.
That’s what most people who are actually making a living think.
But you won’t often see them saying so, because they don’t post at Babypips or in forums generally, or in the comments on Youtube or on the commercial websites so many people use, to try to learn to trade.