Even if Omicron puts fewer people in hospital out of, say, every 100,000 infected, you can still end up with far more people in hospital if the actual number of infected people rises dramatically. (On New Year's Eve, one in 15 people in the UK had Covid. That's one hell of an infection rate!). Take a look at the 'three month trend' line here, to see why the situation is very worrying:
https://postimg.cc/N5LjgDcj
The big increase in the number of people in hospital comes about at the same time as the number of NHS staff off work with Covid has risen dramatically. That's why hospital trusts are now increasingly declaring critical incidents:
https://www.bbc.co.uk/news/uk-england-59866650
It's also why ambulance waiting times have risen dramatically in many parts of the country. If you have a stroke or a heart attack, your best chance of survival is if you can be hospitalised and receiving specialist treatment within an hour at the very most. Many such patients though are now having to wait for more than an hour for an ambulance to turn up and then being held in the back of the ambulance outside A&E for several hours when they eventually arrive at hospital.
Patients with less life-threatening conditions but who might be in agony after a fall are now having to wait over 12 hours for an ambulance to arrive in many parts of the country and, once again, then being stuck in the back of the ambulance for several hours after that.