Many things that were conceptually conceived in the 20th century didn’t become viable until the 21st, such as OLED, VR and AR, raytracing, telesurgery, a whole slew of types of artificial organs, a gigantic amount of miscellaneous advancements in integrated circuit fabrication, alternative vehicle fuel such as methane, hydrogen and rechargeable batteries; maglev trains, innumerable safety improvements in aviation, mRNA vaccines and so on and so forth. I don’t think it’s fair to credit all that stuff to the 20th century, unless someone somewhere saying “be real cool if we could do that” counts as inventing something.