Those who complain about homework, fight with teachers, make it a big issue: US, UK, but mostly the US parents. There were some very supportive parents from these two nationalities though, and they from academic background. Usually nationalities that like homework: Asians.
My work is usually optional. I am talking about middle school and above. For Asians, I guide them where to find extra work and how to approach. For those who fight and do not perform, I bring it to their notice that their kid is very interested in learning, but internalizing requires little more effort.
Learning is a collaborative effort. If parents think that their kid should stop after 20 minutes, that's their choice. I have stopped worrying about it. But many many parents have been requesting me for extra work and these parents are not just Asians but almost from all other places.
I agree with Teacher, the UK parents are mostly unfit to raise kids.

I recall reading Mark Twain and how painting a fence was a chore until children perceived it as fun, then they were prepared to pay for the privilege. Persuasion by example.
So too homework can be fun for children if the right atmosphere is created.
That means no tv or other distractions and time passes slower and homework is completed in what appears to be far less time.
Sadly this is UK today. Best to just give up on these little brats, just make sure they can sign their name so that they can claim state welfare although that appears to created such anguish among the ranks of the long term unemployed it is no longer required.