You have to understand and take responsibility for your strengths in order to be understanding of people who lack those strengths. When I bought into the "intelligence is fake" bullshit, I got really frustrated with people for having difficulty with things that were easy for me.

Intelligence is hard to measure, but it does exist. I mean, think about it. We all know that intellectually disabled people exist, and most of us acknowledge that disability and ability are a spectrum. Why would intellectual disabilities be exceptions? Why would intellectual disability be a binary off/on switch, not a gradient?

And even outside of intellectual disabilities, how are we supposed to help people with intellectual weaknesses if we don't acknowledge that such weaknesses exist?

IQ tests are generally not very good, mind. But they are useful in some contexts. For example, they're often used in testing for ADHD and evaluating what people's needs are by allowing for observation of what impedes them in the tasks and observing the discrepancy between intellectual ability and ADHD related deficits.

It's not necessary for diagnosis, but it can give insight about what would be helpful in terms of accommodations, coaching, etc.

Anyway, it seems like a lot of leftists reject the idea of intelligence because it's an easy way to reject race science and eugenics type bullshit. But it's not really an effective way to do that, because it avoids tackling the actual flaws in those things, and it's obvious to anyone who isn't a leftist that it's a cop-out.

Instead of saying "intelligence isn't real" or "differences in intelligence aren't real", we should be saying "smart people don't carry more ethical weight".