Other places I've travelled by train have lower utilisation of track and rolling stock - so there's more "slack" in the system. The UK actually achieves quite a lot with what it's got.
There are lots of countries in eastern Europe (think of winter weather...) that have similar ratios of trains to routes, but only provide one or two trains per day on each route.
France, Belgium, Spain, Germany &c have a very good network of high-speed trains but this is only possible with much bigger investment in tracks, signals, &c. On Eurostar you can feel
when the train is about to emerge from the tunnel, because it has to slow down for the British tracks.
Also, the UK has relatively optimistic timetables
In other countries it's not uncommon to encounter arbitrary delays just so the train sticks to a more forgiving timetable.