Users as a whole are at fault, and CCP for caving to their demands and replacing spaghetti code outposts with structures. Users are at fault for demanding everything should be destructible. CCP complied with that demand and gave us structures. They anchored capsuleers to certain areas way more than ever before. In the past, people could just decide on a whim – and they did – to move to a different region to mix things up because all they lost were Ihubs. The outposts would still be there when you decided to come back a few years later. These days, you would have to destroy hundreds of billions in rigs when you move out. That’s why sov and EVE as a whole feels so stagnant.
Another reason, which is also related to structures, is the massive proliferation of super capitals and titans. Structures allowed capsuleers to build these in unprecedented numbers and every time something happens, these ships suffocate any budding content at the roots. When CFC attacked CO2 in Fade, the best fights were always those when the jammers were preventing the use of the supers. There were a couple of sub cap battleship fights that were really enjoyable, and as soon as the jammers fell and supers could enter the field everything was over.
Those are the biggest reasons why EVE feels stagnant.