I’d say the larger issue is printing larger parts, not necessarily stronger parts. There are a lot of great, strong materials you can print out of (NylonX, Onyx, etc.), however most print beds don’t exceed a 12" cubed box, so when you start to get to larger chassis or elevator pieces, you have to join together multiple parts to make an equivalent length part, which can start to become problematic.
IMO 3D printing is best when what you need requires complex, non-two dimensional geometry, or can decently reduce the number of overall parts or operations used to make it from other means (milling, laser cutting, water jetting or plasma cutting, etc.). This can include: one piece gearboxes, bearing blocks, spiral/helix elevator spools. wheels, etc.
So for example, lets take a swerve drive. the central module part of most swerve drives (the 2910, 1323 type) requires at minimum 3-4 parts, two wheel forks, a central pulley/ mount that attaches to the large bearing, and sometimes a gear to measure the rotation of the central module on a 1:1 with an encoder. with 3D printing, you can replace this essentially with two parts, by “fusing” the two forks and the central pulley/mount together, and a top part for the encoder reading, reducing parts, likely any complexity from the amount of milling these parts require (2910’s parts require ~2 runs in the mill per part), as well as a reduced number of fasteners.
