According to the ONS, 64% of adults are overweight and obese. To add to that, we have a more aged population than when the NHS was founded. Binge drinking and social drinking are the absolute norm, and smoking/vaping is on the increase (smoking increased during Covid because people were "bored", people take up vaping who never smoked).
People abandon the last bastions of basic daily exercise in walking and cycling, in preference of e-scooters.
A population with an apathetic view towards keeping fit and healthy. The NHS will only get better if a good proportion of the population decide to handle their own health. That seems unlikely to happen.
Go to any gym and see what the very few people who exercise constitute as a workout. Walking on a treadmill for 15 minutes or sat on machines reading their phones. However everybody seems to walk around in athletics / yoga clothing.
Go out for a run and see how many people you see running. Most people you meet do zero exercise beyond walking around.
All the while, every apartment block in our cities sees 20 Deliveroo/Just Eat takeaway deliveries per hour. Restaurant dining is a multiple-time-per-week activity. Salty and oily food dominates in fast food, takeaways, ready meals and restaurants.
This makes people angry because it's the truth.
If you want to see why the NHS will collapse, take a 5 minute walk around any built up area in the UK and look at people's (substantial) guts.