Made worse by the incredible number of factors that GURPS has to account for. Of course the other tactical combat are just as complex and anyone who can use those on the fly wouldn’t be too concerned by the grappling rules.
Fourth Edition isn’t so bad; grappling is taken as an attempt to impede your foe’s movement, so it gives a penalty to his dexterity with the relevant body part, disables some of his maneuvers, and grants you options for takedowns, pinning, and dragging. Other things you can do in a grapple, like trying to disarm an opponent, are handled using the same rules as outside of a grapple. The foe can also counter-grapple you, since grapples are uni-directional, and so you can have states where one combatant has a grapple on the other, or both are grappling each other in the stereotypical “clinch”.
…Aaaand, since half of the fanbase seems to want more detail and realism, a new supplement, called Technical Grappling, is on the way