When CCP first introduced event sites PvP players loved it. Not because it was another income option but because they were implemented as a warpable beacon, were deadspace and cynos were not possible. Eventually they were iterated into stuff like Frostline, which is a shame but not the point of this post.
For those not familiar with deadspace: you can not warp to other players on grid - which makes them ideal to fight outnumberd and pull gangs apart. Suddenly the on grid movement and positioning becomes alot more relevant - no more ceptors burning pings and constant warping of two fleets around each other.
A disadvantage is that warping off because of too much damage is not really an option if you want to get back into the fight, which can quickly move many km away from the beacon while more hostiles keep warping in at 0 - Fights felt more commited, we started to push our ships more trying to stay on grid.
Then we got an even better alternative: The combination of Agency sites and a ESS meant deadspace pockets on demand - with a warpable beacon we can create ourselfes! A huge PvP feature - We could basicly create large FW beacons ourselfes in nullsec.
On top of that it even introduced a bit of map design on the PvP grid - I saw soo much potential in this!
However sadly it was abused with ESS thousands of km away from the warpin just to steal some isk and decleated an exploit.
While not even thinking about ESS anchoring limitations (which are still either in fully triggerd sites, on Jove observatorys or 500km away from deathstar POS setups instapopping you - making them useless as content creators) we now got the greatest FW mechanic removed from nullsec again.
It’s a shame.