3d printing is amazing. It's not a silver bullet, and there's a lot of hype. But it's like any other tool. Put in the time to become proficient and it'll let you do things you couldn't do before. Here's my example. I really like RS-3s, but my Lionels had a very unrealistic set of tanks in the undercarriage.
The real thing looks like:
But my Lionels had a big awkward open space underneath:
So I used Fusion360 (which is free for hobbyists) to model this up:
And when printed and mounted, it looks like this:
I wouldn't have had the skills to scratchbuild that before 3d printing. It's fun to combine hobbies!