Nintendo has confirmed this afternoon that Splatoon 3 owners will be able to access all the basic weapons from previous Splatoon games. This means that you can still rely on your trusty Aerospray or Splat Dualies if you want, though of course, the game will come with an awesome array of fresh new weaponry which may replace your favourites. Don’t forget that if you have a Nintendo Switch Online + Expansion Pack subscription you can now access the Octo Expansion for Splatoon 2 as part of your subscription.
Nintendo announces all the basic weapons will return in Splatoon 3

What do they mean by “Basic Weapons”? Are some weapon types like the Slosher and Umbrella not coming back?
Possibly the most popular weapons.
I think they mean that every weapon type will be returning. So that includes Splattershot, Charger, Roller, Dualie, Slosher, Brella, Splatterscope, .52 Gal, Bamboozler… etc. etc. So expect the basic ones of those to return plus some variations.
There are some stages on 1 and 2 I really loved and hope they bring them.to the 3rd game.
Thats cool and all but give me plants vs zombies vs splatoon instead.