There is only one way to dispel the myth and its to actually count the pages (plus notes on average word count). Its annoying when people use anecdotal evidence and throw around opinion like facts. In order to quantify how "crunchy" or rules heavy a system is, lets go about its system and in its
Options are what fills the Pages of GURPS - options in Ads, Disads, Perks, Quirks, Equipment, Skills and Techniques.
Core System -
3 pages - Success Roll, Contested and Quick Contest Rolls, Reaction Roll and Damage Roll
Characters Rules and System -
2 pages - Character Stats (ST, DX, etc...)
3 pages - Social Background (wealth, appearance, culture, language, rank, status)
3 pages - Rules behind Advantages and Disadvantages.
2 pages - Skills and Techniques
2 pages - Character improvement
4 pages - Equipment, Armor, and Weapons
3 pages - Physical and Mental feats
4 pages - Basic Combat
4 pages - Hit locations, Mounted Combat, and Tactical Combat
6 pages - Injury, Fatigue, and Hazards in general
I've tried using simpler language to re-write the rules of my own game hand-outs and you can boil this down to 1/3 as many words/pages. If I illustrated some of the concepts instead of wrote them down, even less words. Now here is the awesome part - add the pages of these rules to the FAQ and the Errata and then you get the entire bulk Data Size.
The FAQ and Errata should always count towards this.
Of course this all very easy to learn if someone was showing it to you... and many demo and show how simple it can be. If your frustrated or don't get it there are enough who are interested to hang out and talk you through (consider that as way to measure the community).
Martial Arts - more combat options, more detailed rules on many aspects of combat.
Tactical Shooting or High Tech - modern weapon rules and some technique and skill options.
Low Tech - options and most importantly how the technology is used.
Mysteries - some social rules
Magic - adds 10 more pages worth of rules
Social Engineering - emphasis in social campaigns
Mass Combat and City Stats - Macro campaigns - leading armies and nations.
Vehicles - making vehicles
Space Ships - abstraction and simplified ship combat system
Space - more detailes about physics and futuristic games.
OPTIONS per Book Gaming Model
The Options per Book is a great model that DnD was already pulling off that was later Refined by WOTC as a great money making engine. Options per Splat Book creating more nuances in essentially stuff you already have. I remember when Sword and Fist first came out, and how successful it came to be which became the standard marketing for a lot of games: Sell Options to Players and secondarily the GM. Many game systems followed suit.
Now You may be overwhelmed by GURPS and Martial Arts but note how Two Books covers, one being the Core Books, covers so much of Martial Arts and draws from Historical and Real World martial arts. It also gives you tools to make your own stuff. If we are inventing stuff, I don't see the difference between the game designer and the hobbyist (which is a Courtier's Reply a kind of fallacy about the source). So yeah - GURPS gives you a lot of your not burdened by Bias for Authority - and a lot of Non-Game writers produce awesome set of rules and material which they share for free (my bias is to whats FREE).
The trade off for all those options being in a couple of books than buying them bite sized is that there is a lot and one may feel obligated to read them all. If your getting value for money, I don't think one should be complaining that they got too much value. I think the writers did their job and the reader just needs time to digest - and its not even that hard of a problem when there is so many friendly gamers willing to share their time to help others understand. Take the Mook's stuff for instance and the bradley harvey's gurps youtube stuff and many others.
In the end learning can be very easy, if you're busy google someone to help you learn it.
Options and Implied Rules, the EUA for Players
If you're a GM and you want more realism, GURPS is not only your friend it is that End-User Agreement thats biased towards you. Its already in the book that you can pick and choose what ever rules you want, but what is great about it is that the Near-Realistic Baseline is the Implied Assumptions at how challenging the GM can make it.
When a new set of rules come out, its a modification to the EUA between players and GMs. When ever someone chooses an Add-on Book, that's an EUA modification as well. If you are a heavy modder, that's parr for the GURPS course. There is no STAMP of SJGames approved needed, if it makes sense to you and you guys have fun and there is no Stigma for heavy mods as the rules are really very modular.
You don't even need to read the other rules, and most people don't. When I did my flow chart of GURPS rules I noticed there are many rules that would be nice and can bring a lot of realism. In face to face, with apps, spreadsheet and some automation they are great but in my current automation I use most (automation via Roll20 Macros)