What ue4 uses has nothing to do with anything.
You can make it use whatever system you want like every other engine in the history of engines.
A dedicated server is literally useless in 2021. It will only run up your bill and reach player cap and an atrocious lag over a single launch weekend.
Peer to peer isn’t limited that way, as anyone can be a “server”.
You can think of it as hosting a LAN party if you will.
Almost all games with servers are dead or barely making ends meet.
The other points from @Nawrot are true - a proper in game communication system would help most games.
However this is a shooter, so it’s not an mmorpg that needs this as a core feature since you want people to party up for raids and such…
Take rocket legue as simple example.
I believe that it works by instantiating a server instance on your machine if you launch a game, or letting you join someone else’s match…