Vaccine passes - just went to the theatre in London and I showed mine no problem. So big events generally have them. Everyone needed to (or a negative LFT) and they were pretty hot on doing so.
Read the Emily Sheffield article I linked. Your experience at the theatre is an exception in England.
In other countries including many in Europe, passes are required for restaurants, shops, cafes, etc.
They're also not pussy footing around with vaccine mandates for the people working with the most vulnerable - health and social care workers.
The UK, or at least England, is only weakly at best enforcing masks.
And you ignored the last mitigation I mentioned. Ventilation - HEPA filters or the cheaper DIY corsi-rosenthal boxes.
Still, I hope regardless of everything else, that you enjoyed your trip to the theatre. It's good to (safely with appropiate mitigations) support the industry.