A reliance on vaccines as the foundation of the modern approach. And also a consequence of the world having gone through multiple pandemics in the post-war period that health services managed to cope with to one extent or another. The 'modern world' hadnt had a really bad pandemic, which is why up until now everyone was still using 1918 as an example of a really bad pandemic.
One consequence of that was that many of the crude, draconian measures that can be employed in epidemic controls were considered not to be worthy of being in the A plan in the era of modern medicine, science and technology. When doing pandemic planning it was still deemed appropriate to include nasty pandemics with difficult mortality and hospitalisation rates, never mind that the systems and plans would not cope well with such scenarios if there was no quick vaccine or antiviral available. They would at least demonstrate that they had not forgotten to include such bad scenarios, but there is a difference between including them and formulating a response thats actually fit to cope with them.
The 2009 pandemic, despite initial worrying mortality estimates from an early outbreak location in Mexico, didnt end up having a mortality rate that would require a very different response. And its other burdens on healthcare were also much reduced by the fact that certain degrees of immunity against it appear to have been present in older people.
The main reason I even bothered to mention 2009 swine flu pandemic a bunch of times on this forum is because some fo the details in terms of how the UK responded to it give clues about the standard orthodox pandemic approach, and certain UK quirks.
For example an early phase of our 2009 response was labelled as 'contain' and consisted of contact tracing and attempting to use tamiflu in an unorthodox manner to suppress infections stemming from these early cases. But it was misleading to call it a containment phase because actually it was a delay phase, there was no expectation of actually containing that strain of influenza and preventing an epidemic here. Rather they just wanted to slow it a bit, and to find enough cases that they could study closely for clinical reasons, ie gaining data in a FF100 (first few 100) study.
The approach was similar this time (minus the tamiflu), until it wasnt. Which was only just over 2 weeks ago.