What's up in M +18?

So I smoothly went my way to resil 17 this season, pug only. Most runs turned out really well, there weren't many "WTF - What did I just witness" - moments during my journey I can remember of.

Also: Invites to other people's keys didn't take long for me.

Now applying to 18 keys, two things changed:

1. Invites take aeons. People seem to get really picky all of the sudden. Why wasn't this the case at the edge 15/16 or 16/17? I really had to finish resil 17 before people start to invite me to 18 keys I timed with 5 or more minutes left on 17.

2. The number of easy mistakes players, especially tanks do is getting absurd. I'm not talking about hard pulls, where everybody struggles to stay alive and keep interrupting / stunning the best he/she can but eventually there's a bad overlap. I'm talking about tanks dieing in split seconds (so not using proper defensives), people standing in big aoe or healer who don't know how to time their CDs.

Will this get better somehow (I guess not)? Is there anything I do wrong somehow?

And if not, I'm really sad, Blizz raised the bar to 3.6K forytu achievement, forcing us to finish 4x 18+ :(