Why is the best advice study the endgame?

Frankly I love playing and studying endgame theory .

However seeing as it comes after the opening and middlegame why is the advice to study that first.

Hello

"In order to improve your game you must study the endgame before everything else; for, whereas the endings can be studied and mastered by themselves, the middlegame and the opening must be studied in relation to the endgame." - Capablanca

"Ninety percent of the book variations have no great value, because either they contain mistakes or they are based on fallacious assumptions; just forget about the openings and spend all that time on the endings." - Capablanca

Endgame study is good 4 learning cheakmate patterns and king activity

The endgame is a better starting point as fewer pieces on the board, fewer calculations to make.  

Opening is learning the basics eg take the center, devalop your miners, king safety and conect your rook by......well you get it

Now the middle game is key its about not making the same blunder again and again and if you focus on just not the same mistakes over and over you will improve its prob the most simple but important thing u can do