Opening study is more popular. It's immediately applied to the student's games. Endgame Skills are used on occasion. Games are generally over within 25 moves. With an easy winning endgame.
Opening Study vs Endgame Study

My skills 100% opening, but the only thing I know about opening is horsey go before bishop .
I started reviewing some endgame stuff after reading this thread and I am starting to see how important it is.
I understand that at my level the most important thing is blunder checking but how do you study/practice that? It's not like you can read books on how to not blunder. I think you just have to play a lot of games and review them so hopefully you stop making the same blunders?
If I can just remember to check the diagonal squares the opposing player's bishop covers before I move my pieces i think it might get rid of 50% of my blunders...
You answered your own question. If you blunder, what was the blunder and why did you make it? If you hang your piece to bishops all the time and you recognize this then you're already diagnosed the issue.
For example, in a game I just now played I made a gross blunder (which my opponent did not see fortunately).
I missed that my opponent can desperado their queen. The key to avoiding such a blunder in the future is recognizing the situation with both queens under attack and making sure to check if my opponent (or me if roles are reversed) can move their queen with a bigger threat and/or piece capture. The best way to do this would be to drill tactics involving queen desperados to make these situations more intuitive in the future, rather than just trying to remember the next time I'm in the same situation. Therefore, if you want to stop blundering to bishops, do drills involving bishops.
My skills 100% opening, but the only thing I know about opening is horsey go before bishop
.
I started reviewing some endgame stuff after reading this thread and I am starting to see how important it is.
I understand that at my level the most important thing is blunder checking but how do you study/practice that? It's not like you can read books on how to not blunder. I think you just have to play a lot of games and review them so hopefully you stop making the same blunders?
If I can just remember to check the diagonal squares the opposing player's bishop covers before I move my pieces i think it might get rid of 50% of my blunders...