It's Just Roll 3d6

Some people play GURPS by just "rolling 3d6." For example, in a d20 game where the group does not care about the rules, they ignore most of them and "just roll a d20." Character creation only exists to generate skill and ability levels, and 90% of the rules are ignored to just "roll 3d6" or less for things that come up during play.

This is the GURPS Lite model of play, where the Lite rules are just a system to generate skill levels, make rolls, and run a simple combat system. Most GURPS groups stay close to the Lite combat system and ignore most of the book's advanced (and optional) rules.

Attack with a sword? Roll 3d6. Did you hit? Damage minus armor, next player goes.

GURPS is as rules-light as you want it to be. You can get in groups and games that make you feel you need to follow every wounding rule, every by-the-book modifier, and every "how to play this right" sort of feeling coming at you - but in practice, you really don't need to live up to a "perfect play" standard in this game. This is an old-school game, and the rules are suggestions.

Is there always a by-the-book way? Yes. But, from the How to Be a GURPS GM book:

Everything in GURPS is optional – we say so all over the place. We specifically say things like “as long as the GM is fair and consistent, he can change any number, any cost, any rule,” “everyone must realize that an epic story is apt to transcend the rules,” “don’t let adherence to a formula spoil the game,” and “if there is only one ‘right’ answer to fit the plot of the adventure– then that’s the answer.” The rules are only there for when you need them to help advance the game. Most of the time, you should be doing that by talking and roleplaying and telling a story.

Make a ruling and move on. You, your group, and your game will be fine.

You will also find GURPS to be much more flexible than your average 5E game due to the above.

GURPS Lite is all about efficiency. It follows the same 'gameplay loop' as a d20 game but without many action types and bonus actions that can bog down a 5E turn and drag out combats. The one-second combat turn in GURPS Lite is a game-changer, allowing a single action to significantly accelerate gameplay. In contrast, games like Pathfinder 2 and DC20, with their three and four actions per turn per player, can lead to a sluggish pace as players strategize and execute combos and multi-attacks.

Consider this: in GURPS Lite, a simple action like 'I draw my sword' or 'quick draw skill roll and attack' can be executed in a single one-second turn. Compare this to the time-consuming process of planning movement, a spell, a few attacks, another action, or any combination of three or four actions during a turn.

The time taken during a turn in tabletop games is directly proportional to the number of actions allowed, squaring the time taken to the number of actions allowed. One action takes one unit of time, two actions take four units of time, three take nine units of time, and four take sixteen units of time. One-action and one-second turns are the peak of efficient game design.

When you determine that each monster has multiple actions during a turn, six goblins now have 18-24 actions for the GM to decide every turn (and roll for!). Where do people find the time to play these games? They sound great on paper, but I doubt these games can be played quickly. They make B/X and GURPS look like rules-light games during play, which, comparatively, they are.

Modern games love to "ignore the referee" regarding ease of play. While character creation is straightforward and fast in many d20 games, the time taken per turn is atrocious and a complete slog. People think GURPS is a slog during turns, but it isn't. Character creation is the slog, but this is why we love the game. No game gives you this much control and customization.

GURPS skill rolls and combat turns are no different than a B/X-style game. In most turns, you decide on an action; often, you don't need to roll for it - just say what you do.

Also, with a one-second turn, there may be long pauses between attacks. If you watch modern battlefield footage, count the seconds between shots soldiers take. In many cases, there is a 1-6 second delay between every shot (or even 2-12). Not every combat will be this "video game alpha attack," where an attack happens every second.

In many cases, "do nothing" is a valid turn action, especially for untrained fighters, and it is also pretty standard in real-life warfare.

If you are doing a "dungeon combat" and have a bunch of goblins, you could roll a d6 for each one of them and delay their actions, or a d3 if they are more skilled at battle. Goblins engaged in combat on the frontlines would attack every second, but the ones in the back would often delay actions randomly. Even an archer supporting the frontline troops will delay firing for the best possible shot and throw in an aim action or two as they wait for an opening.

Those delays also open up opportunities for players to roleplay. What do you do if the battle quiets a few turns while everyone repositions? Demand surrender? Surrender? Propose a truce? Disengage?  Refortify? Intimidate the enemy? Bring up a heavy weapon or call for help? Ask for help against a common enemy? Offer gold to stop fighting? Does the enemy make those offers? Combats may not last "until death," and in many real-world fights, this is true, too.

Also, the best possible action isn't always what happens. A few goblin archers may fire arrows down a hall to deter movement. They may shout insults, bang drums, or hide to wait for a better opportunity. They could throw food, rats, or chamber pots at the party. They could be arguing with each other. These "delays" are great roleplaying moments with a lot of personality. Not every enemy is this "programmed AI bot" that moves towards every enemy and attacks at the first chance like a computer controls them.

This happens with modern d20 games, where multiple actions encourage "micromanaging and optimizing turns." These games are based on card-game design, not reality. GURPS is reality-based, and the dis-optimization of player and enemy actions increases the game's realism. It feels incredibly counter-intuitive, but it makes sense when you step back and consider real-world battles and hand-to-hand fights.

Wake up from this modern d20 gaming "mind lock" of turn optimization and to-the-death battles.