"I really don't care about the details. In my experience, Intel graphics has only ever been good enough to get a computer running until I can slot in a true graphics card (Nvidia or AMD, given the moment)."
These first generation AIB cards from Intel weren't bad. No, they couldn't face the best AMD had to offer (nevermind NVidia) - but they weren't bad entry cards. At the very beginning they had a ton of drivers and optimizations problems - but they did their homework, and this isn't a problem anymore.
If I remember correctly, their ARC770 would be about the same level of one RTX3070, maybe one 3060Ti. Far from stellar, but not bad per se either. After all, I'm running one RTX3060 (non Ti). As are about 5,86% of Steam gamers this month. And this is the first more popular graphics card on Steam survey. The second one is... RTX4060.
They had a good video encoder too, and supported AV1 hardware encoding when no one else did (NVidia started hardware AV1 encoding on the 4000 series).
To me the reality is simple: it was a first try, people were scared and money short, they had a lot of teething problems and although "everybody" buys something around the 4060/4070 series, reviewers praise the 4090 monsters. This steer people away from what they would realistically buy. Who cares if the 4090 is (say) 3x faster than the 7900XTX? I won't buy either! What matters to me (to vast majority of buyers) is what is the better: RTX4070 or 7700XT?