For example, I remember frequenting the NerfHaven forums back in the day, and people were designing Nerf blasters in Solidworks, printing drawings out, gluing them to polycarbonate, and using scroll saws to build their own blasters capable of 150fps. Nowadays, I can buy a printer, a hardware kit, and build my own 200fps capable blaster in an afternoon, and there's probably 5-10 new interesting, fleshed out concepts a month.
The explosion in depth, detail, and accessibility in DIY cosplay designs is also incredible.