Why not just long index? they go up for a century

This has not to do specifically with Forex but trading in other instruments.
My question is:
Why am I trying to predict what will pairs do that go all the time up and down? Stock Indices like DJI and S&P go bullish consistently for 100 and 90 years respectively. Check pics attached,
Why can't I just attach an SMA/EMA 50/100/200 or whatsoever MA/period and just open long positions when it goes below the MA and wait for it to go to new ATH? Why should I bother with FX Pairs that don't go only one way for a century? Am I missing something? Looks WAY TOO MUCH EASIER than forex that goes up and down all day every day.

historic annualized average return of around 10%. So if your ok with average 10% a year that's a decent way...also realize if you try to pick tops and bottoms you will make less and average institutional trader cant beat S&P500.

I don't mean like "buy and hold it for the whole year" style.
I mean like going on the M15 M30 chart, attach a 50-EMA and open buy orders when price goes below it. It's much faster than the "buy and hold like invest style" and produce more than the 10%.
Wouldn't that work? Why bother with forex that you don't know the overall longterm direction

yeah but there are periods where index correct for years...You could be losing for a long time just going long.

Look at the s& p 500.. weekly

It's a good enough idea.... except "when price goes below it", wait for price to return to long - and then buy. And if you're watching on M15 M30, then I would look at M1 and M5 for a return to long.

that could make bit smaller profits but indeed would reduce the DD and will be safer not to bust the account. Or you could just go long when it's above the MA. No need to wait for pullbacks or them to finish.