There's GURPS, and then there's GURPS
I've played GURPS since it's first (medieval combat only) version came out in 1985. I've memorized most of GURPS 3e and have had lots of success running GURPS for new players. But even I find the 4e Basic Set a bit overwhelming.
Even though most of the core rules are very similar to the core rules of the 1986 1e Basic Set, because the 4e Basic Set really embraced the U for Universal in GURPS, and worked in most of the rules for supernatural and inhuman traits from the countless GURPS worldbooks that had come before, and also went further with the G for Generic in GURPS and added systems for modifying traits and working out what the point costs ought to be. The 4e Basic Set is over twice the length (~576 pages) of the 3e Basic Set (256 pages, 30 pages of which are basic Magic and Psionics systems rather than core rules), and most of the added content I never use, because I run games in low-tech worlds with pretty standard humans and fantasy races.
The 4e Basic Set is a great toolkit for designing almost anything, but it's got an awful lot of noise in it if you're a new player just looking to learn the rules so you can play a character in a game. Especially if it's just going to be a normal human character.
That said, I do have several suggestions for how to make even GURPS 4e accessible to new players, if you (the GM) have learned GURPS 4e already. Pick and choose any or all of these.
First, choose a game setting and type to run.
This will limit what the game will include to what is relevant to creating characters for that setting, and what will be used in the first sessions.
You might want to choose a relatively simple context to start with.
Something that greatly limits what there is to think about, but is still fun.
Warn players about the seriousness of combat and the importance of what characters do during combat.
Explain to them what combat gameplay and tactics are like, so they don't put a lot of time into creating a character and then do something foolish in combat that is likely to get the character killed or maimed right away. And let them know that it's possible serious injury or death may happen anyway.
To that end:
Run a fun short learning game...
... that may not even be part of a campaign you want to run, with characters made just for that game, that aren't expected to necessarily be used later, where serious injuries and deaths are expected to be likely during the learning session. A brawl where most characters involved have few or no unarmed fighting skills is a great simple starting point that can nonetheless be very fun, and is also a baseline thing to have experience with. A low-tech arena combat is also a great choice. If you're going to be doing gun-type combat in your campaign, you might start with a simple gunfight situation.
Have a bunch of characters pre-generated that players can use instead of building a character-
or that players can use as examples or starting points to modify to make their characters.
Prepare an introduction packet for the game you want to run.
It can be half a page, up to several pages. Explain the campaign setting briefly. Explain the intended style of play briefly. Then list what the choices are for new characters in the campaign. This will be a much much shorter list than what's in the Basic Set. You may also list various appropriate backgrounds (Templates) and what characters with that background have. Then character generation is mostly about picking things from your intro packet, not swimming through the 4e Basic Set or other books choosing from a universe of choices most of which won't fit your game anyway. Probably they can create a character with just the free GURPS Lite and your intro packet.
Be available to create characters with the players before play starts
Mentoring: a little goes a long way.
During play, I have found anyone can play GURPS ...
if you explain situations and options to new players in terms of the gameworld situation, in natural language, not game terms.
Then let them tell you what they want to do in game terms, and if they're interested and ready to learn game mechanics, you can tell them how you're converting what their intention is to game mechanics, in as much detail as they are ready for. This works well because one of the great things about GURPS is that the mechanics are based on trying to represent the game situation directly in ways that make sense. Every game mechanic represents something relatable and logical. So you can start by describing the situation, and work a new player up to understanding how the game mechanics model the details.
Resources
The free GURPS Lite rules contain the basic core rules of GURPS.
Some people even play entire GURPS campaigns using just the GURPS Lite rules. (As someone who loves the detail and especially the hex-based Advanced combat system, I'd never do that myself, but many have done that, and it's not a bad starting place, especially just as a first thing to read to understand what the core came is.) The 3e version of GURPS Lite is somewhat different and is also recommended for learners despite being out of date for 4e.
This features posts for new players, and more advice and resources on introducing GURPS to new players.
