I was at a talk at my DD's school in October about UCAS as she is currently going through the process. The woman who was speaking was from Glasgow Uni, she was speaking about the process in general, but also shedding light on that her uni look for in personal statements. (with the caveat that other unis may do things differently, she could only talk about Glasgow).
Anyway, she said that for medicine, dentistry, vet med, law - they will ALWAYS read the personal statement. She said that they are looking for an applicant to tie it all together, not just reel off a list of what they've been doing. She said - don't just tell us you have been volunteering in Oxfam or playing rugby, tell us what you have learned from that experience and why/how it contributes to your decision to study what you're applying for. She said they always wanted to hear about part time work even if it's not directly linked to the course you are applying to.
She also said that in some departments they are not interested in personal statements. That you are likely to get an offer if you meet the entry requirements and nobody cares two hoots about your Gold D of E or weekends mucking out at the dog rescue.
But that the important thing is to tie the statement all together as one - apparently lots of applicants just list all their extra curricular stuff they do without saying why they chose to do it, what they learned, how it has broadened their outlook.
My older DS applied to uni for 2021 entry, he was the covid cohort so had pretty much nothing relevant to the course he wanted to do (science based) as all volunteering and internships stopped. 5 unconditional offers. So I would say do not get hung up on filling your child's every single waking hour with sport and music and volunteering, let them explore interests and encourage them to think about what they are getting out of their extra curricular, and how to express that.