They live in the 'here and now' world of sensory overload.
No time to think, learn, and plan a future.

I grew up in a country town before TV reached it, and slide rules and log books were the high tech tools you used in school.
No cell phones, no computers. No calculators.
It helped.
Plenty of time to study, think and make plans for a future.

But I'm sure teachers will get the blame. They always do.

I'm not a fan of mobile phones in schools, but I doubt we can blame that for keeping students from learning math and science. Good teachers can make a tremendous difference in students' eagerness to learn the material. And hiring good teachers requires funding, pay, benefits, etc.

I'm 40 and many of my high school classmates wanted to become teachers as a career aspiration, and did. Not sure that's the case these days with book bans and loony parents in the US. Not sure if they have similar problems in other developed countries. Developing countries prioritize math, science, reading, computer skills, etc. And teaching is still viewed as an aspirational profession that kids want to get into.

I sub-teach and the kids were off the rails in the middle school where I work.

They refused to do the work assigned with a few exceptions. They refused to put away their cell phones and watched videos and texted for the 40 minutes of class. And they knew I couldn't do anything to change their behavior. They knew the administration couldn't stop them. They just weren't interested in learning anymore.

I believe you've seen what you claim, just saying it's not universal.
Of the 16 or 18 schools where I sub, I've noticed only one that could reasonably be termed "behind pre-pandemic".
When I do math, the same stuff is covered now as in '18, '19, & '20 before the schools closed.
I don't do any language arts, so I can't speak to reading, only math & science.