Pub issues need a thread to itself. Change of social attitudes such as not being allowed that 5th pint if you drive, there have been issues regarding law changes, supermarkets being allowed to sell alcohol. Umpteen reasons.
It is possible the problem may be worse where a larger immigrant population, that don't have nights at the pub culture, have become dominant.
A younger generation more inclined to go to the city for trendy bars, and avoid traditional pubs to socialise, doesn't help. Especially if they can go on to clubs.
It has meant, for a long time, that there is insufficient custom to keep places going and they are worth more as land value than pub. I don't think we are as socially aware as we used to be. You might know your neighbour but are unlikely to know dozens of folk in the neighbourhood you chose to meet up with at the local watering hole.
Those that survive often do so on the food service, many of which simply buy in ready made. Lucky you if you find one with a good resident cook. And many are so food oriented you feel you are intruding if you wander in for a quiet pint, like none of the tables are really for you as they all have menus and condiments and possibly cutlery. Doesn't encourage regular visits.