N64 NSO is coming out as slowly as I'd expect it to given it's the second year of the service and the available pool of N64 games has never been very big, even back when it was being sold piecemeal on the Virtual Console (NSO's library of 31 titles is 10 titles more than either the Wii or Wii U had, even considering the 4 or 5 titles NSO doesn't have). Going by the fact that they've added another Rareware title for the launch of the Japanese 18+ app, can probably expect a couple more of those to come out this year, but I think we're going to get another 8 titles max this year (think it's quite likely that we're getting Smash Bros and Donkey Kong 64 but the rest is very much up in the air imo.). It also still needs to make its emulator less rubbish, because while it's still an improvement on the state it was in at launch it's still in need of improvement.
imo the main "why is this coming so slowly?!" is the Game Boy and Game Boy Advance libraries. They're massive! Even considering purely first-party stuff they can easily put on there there's a good 50-70 titles they can put out on each one, yet GB NSO's only getting updated when they're updating the base-tier NSO apps (and those got a decent amount of titles during their first year), and GBA's sharing the Expansion Pack slot with the N64 emulator (and getting the exact same amount of titles afterwards as it's getting this year, but imo it's getting a better deal than GB NSO is rn). Bring on the first three generations of Pokémon! Super Mario Land! The other 3 Wario Land games!