>>47835573Route 23 is obligatory even by your stupid standard of Kanto being just optional post-game (which is bullshit, as the ultimate objective of the story is to beat Red).
The only truly optional areas in Kanto are:
-Mt. Moon
-Rock Tunnel
-Route 3
-Route 4
-Route 5 (only if you decide to go to Cerulean via Rock Tunnel, which is otherwise optional)
-Route 7 (only if you decide to go to Fuchsia first from Lavender and then to Celadon via Cycling Road)
-Route 8 (only if you decide to go from Cerulean to Lavender by otherwise-optional Rock Tunnel)
-Route 11
-Route 12 (if you decide to go to Fuchsia by Cycling Road)
-Route 13 (same as above)
-Route 14 (same as above)
-Route 15 (same as above)
-Route 16 (if you decide to go to fuchsia via Silence Bridge)
-Route 17 (same as above)
-Route 18 (same as above)
-Route 19
-Route 22 (you can access Mt. Silver from Johto side)
