Pure vanilla hacks like RTDL with long lenght are hard to find but there's a lot of long choconilla hacks in the site.
Choconilla are hacks that uses vanilla gfx for the most part butvhave custom music, sprites etc. or sometimes they just use custom paletes and music.
I can recomend you these hacks:
-Another Mario World 1 and 2(the first is a pure vanilla hack and the second is vanilla with only custom music and paletes)
-Vanilla Level Design Contest 7,8 and 9
-Classic Mario World 1,2 and 3
SMW The Princess Rescue 1 and 2(those are my hacks, they are all around 113-120 exits)
-Bowser's Cataclismic trap
(great hacks by Gamma V)
-The new Mario world
-The 1st Old-School Level Design Contest: Collaboration Hack(both are pure vanilla hacks)
Mario's Enigmatic Tales 1: The Betrayal
Mario's 2 Ways 2 Victory
Super Pika Land Ultra: Vanilla Version
Rise to the Challenge