They were never that good. They are a 'meme' band. Some sideshow 'hipster' movement found them cool. They are a brand. One or two albums, great. Interesting. Maybe. They don't make any more decent music so it's natural to break up if there is no reason to exist. Unless they can milk their fans for a generation and let them relive a few moments ...
Sure, they were never huge and perhaps never that good, despite the fact Johnny Ramone makes many top N guitarists lists and the band is consistently ranked top N for both music and influence.
The 100 people who bought their albums created 100 bands. The influence of the Ramones can't be overstated.