TL;DR: It’s a co-op roguelike. Drop in, explore the map, survive 3 days and beat a unique boss.
Once you buy it you get access to the complete package, and there are no battle passes or microtransactions to contend with. It can also be played in singleplayer should you wish to stay offline, with enemy health pools that scale down so that it’s not too overwhelming for solo players (although curiously, there are currently no plans to allow players to play in pairs).
You either didn’t get past the start screen, or you’re trolling.
Elden Ring is an evolution of the Demon Souls formula, but already with large changes. Sekiro is completely different.