Of course they are good enough.
Med schools each use different criteria, not least because they don't all want to be selecting the same applicants. Some focus on GCSE grades, some on performance in aptitude tests, some on PS and references.
Some medical schools use GCSEs as a minimum achievement, as in they won't look at you unless you have a set level of academic achievement. These will be on the individual websites, and are normally some way short of 7As. DD narrowly missed an interview at Nottingham because she "only" had 7As and an OK UKCAT result. Birmingham is another that looks closely at GCSEs, and last year demanded A*s in English., Maths and Science.
The thing is to be tactical and play to your strengths. Voluntary/work experience can count for a lot in some places, aptitude tests matter more and more. And worth noting that Cambridge give out some tough offers, up to 3A*s1A at A level. And accept that it is a bit of a lottery. DD reckons she was rejected at one place because of one poor interview out of nine. Virtually no one gets four offers. The good thing is that to some extent it does not matter where you go as you end up with the same qualification.
DD was happy to take a gap year so had one aspirational (Bristol - it may have the highest ratio of applications to places and sets a relatively low bar for both GCSEs and apptitude test results) and three where she felt she met the criteria, and they met her priorities (teaching style, city campus etc). Had she had to reapply, and depending on the grades she got, she would probably have continued with the one aspirational (perhaps Oxbridge) and a couple of less popular choices.
But I agree with other posters. Cambridge will offer all sorts of stuff, but is not automatically the best choice. It has a trad teaching style, it has shorter terms, and places like Imperial/UCL may have more cutting edge research going on. It is also a six year course, whereas DD will be doing a five year course with the option to intercalate, not necessarily at the same University, in something she chooses, half way through. Some may also find they are in the bottom third of the cohort surrounded by some extremely able and hard working peers, when they may have been happier elsewhere in the top or middle third of the chohort.