Not really showing the US system proud if you think the OP can be seen as an 'innocent question'. Also, really surprised it took 15 years when issues around grades (letter or numerical) are so often in the news.
I also found the grading system confusing when I moved from here from the States, though comparing between US districts has its own difficulties before comparing with any part of the UK. The systems are just too different. Any flips between the systems are going to be more on individual circumstances rather than anything definitive about the systems as the disjointed whole they are.
I don't get the assumption that it means standards are low though -- especially not with the on-going conversation in the States and data on US grade inflation that's been going on for a good couple of decades now. It's in an entirely different league compared to what's commonly discussed with GCSEs and A-levels (and even less with other qualifications). The same differences can be found when comparing between different US districts that use different grading systems. The same competitiveness about ranking can be found in many parts of the US (which is one of the factors in why schools in well-to-do areas have a higher rate of grade inflation in the US than other schools - parents push for it, less easy to do that in any of the UK systems with more outside grading than common in the US). Also, the same defensiveness, though actually I find Americans far more defensive, especially about people outside of an area, calling something low standard. Far quicker on the 'don't like it leave/glad you left' than anything seen here.
Also, the definition of "good university" is subjective, it depends on what one wants out of a university, the subject (I know there were some claims earlier this year that the COVID changes to the system were going to be the death to old poly-techs, but in some subjects, they're among the top institutions), and many other factors. Yeah, there are a lot of really competitive schools in both the US and UK that require a shit-ton of qualifications to have the slightest chance, but there are good schools that don't have as many requirements or are more willing to bend them on interview or supplement information for someone who doesn't hit all the grades or test scores. High specific requirements and rigidity on them doesn't automatically equal better, I think the push for kids to need to do all the things to jump through hoops is a detriment to young people and education and this so much worse in the US. I graduated high school with someone who went to Yale and someone who went and now teaches at Harvard medical school and...if that's high standard living, I'm quite happy not to be there and not put my kids through it.