Are there any full bands from 2015 or after?

Do you mean that formed from 2015 on?

Greta Van Fleet

U2

Theory on the evolution of music.

Jazz is easier to make-produce than big band music.

Rock and roll is easier to make-produce than jazz.

Rap/Solo singers music is easier to make-produce than rock and roll.

Just like improved everyday products, easy trumps.

Big Joanie
Electric Octopus (instrumental band)

There are plenty you just need to look outside of the mainstream and Top 40.

My favorite rock bands with post-2015 activity:

The Sea and Cake https://youtu.be/nKdPuqxbwP0
of Montreal https://youtu.be/AdRtEDdFOR8
Deerhunter https://youtu.be/XB7-XVibmbM
Deerhoof https://youtu.be/pIq5na-4JkE
Radiohead https://www.youtube.com/watch?v=kPAZV8y4B44
The High Llamas https://youtu.be/OaJOt_DozfQ
The Flaming Lips https://youtu.be/DgWaChX1cno

Just to put it out there. Wikipedia has a lot of information if you do a search on "[year] in music" You'll find a newly formed band section for each year and there appear to be a good number of new bands for 2015 and 2016. I didn't look at other years but yeah, there's a number that seem to be your traditional 3/4 piece rock group types. So it's not a dead form for a band but I think finding materials by these bands is going to be rough since there's no real place for rock breakthrough hits anymore just by the virtue of how today's music distribution works.

I personally don't listen to rock like I use to so I haven't sought out any new rock music in some time but it looks like there's new stuff to be found if you actively look for it.