Length doesn't really say anything about scope. I can take MIT license, one of the smallest and most permissive license out there, and add a single word which would make it incompatible with every other license in the world including itself.

The only saving grace with FLOSS licenses is that they are not contracts, and only impacts those who seeks additional permission to distribute copies of a copyrighted word. If someone feel they don't understand the conditions which the license automatically grants permissions, they can always go directly to the author and ask them.

Yeah, but the GPL is a pretty standard license and as such has many summarizations and tl;drs floating on the web.

With company legalese, everyone has its own...

An end-user of software licensed under the GPLv3 doesn't ever have to read the license until they decide to modify and share it.

At that point they should be well-versed in reading licensing agreements because they're touching others' source code.