Three weeks. Three more weeks.
I'd argue this game is incredibly different from the other smash games, purely due to "Everyone is here!"
This game had 4 years of dev time, but most of that went to making sure every vet came back. They wanted that to be the big selling point of this game, that nobody had to drop or learn new characters because literally everyone was back.
Because of this and obviously implementing Spirits/World of Light, there was much less time for newcomers. Whereas every other Smash before this one largely focused on newcomers, instead this Smash focused on characters coming back, big names especially such as Snake, Pokemon Trainer, and the third parties from Smash 4. This is clearly a huge tone shift from the older games.
I think it's completely fair for some people to feel disappointed in this, mainly because they wanted to see newer characters and new movesets, but of course you can't win everyone over. That's why for the characters we DID get, they were either huge wants from the fans (Ridley, K.Rool) third parties with widespread appeal (Simon and Richter, Ken) and well known first parties (Isabelle, Incineroar). Echoes were just a bonus with the limited dev time they had to give something extra for the fans.
"Everyone Is Here" really changed everything for this game, and that's what largely made it different from previous entries.