I agree gurps might scratch your sweet spot.
But for something cheaper I suggest you try battlelords of the 23rd century. Honestly it checks all your boxes and in some ways better that gurps.
Foremost, you want a game where builds and tactics matter? In very few games do they matter like they do in battlelords. You can, and should, spend hours building a character in this game. It can take a while just to pick out the right suit of armor and helmet for a character. (Not being armored is not viable) Noobie hint:take a TDA helmet, it's reasonably priced and protective, and gives you a 15% targeter bonus to shooting. You can't beat the threshold 5 Bear armor.
Once you have armor, you get to look for options to install into it. One should be a gyro stabilizer in your dominant arm, it gives you a 10% bonus to shooting as it makes your weapon count as braced.
Then you pick weapons, and there are a good number in your basic set.
Then you pick gear. There's lots if this. Sensors, comms, armor coatings, medical gear, weird stuff, there's a huge list too.
Honestly the squishy bit inside the armor is the last thing you should build. Pick the gear and weapons you want to have, then build a character to use them. Hint. Pick a human, they seem kinda meh but they have by far the highest skill points in the game and skill points matter.
Tactics, you said? Yeah, they matter. At least one player per team must have a weapon capable of threatening heavy (threshold 7+) armor, even if he has to spend most of his money buying it. A medic is good too, even tho everyone should have a healing injection called a BRI. A guy with good sensors and comms can be good too.
A grenade launcher loaded with smoke rounds is a good idea too.
The basic system uses d100 rolls based on half the base attribute, 5% per skill level, ranged combat uses the weapons accuracy at the target range, plus bonuses for equipment like targeters and stabilizers, aiming, fire mode, etc.
The basic rules ARE simple, honestly. You have your base chance, half your stat plus 5% per skill level. After that it's just simple math, addition and subtraction based on modifiers. I will not deny there can be a fucking fuckton of mods, tho, but it's all just addition and subtraction.
No luck points, no 'woke' (honestly can't we have one fucking game thread without that shit?) I can honestly say gamer to gamer it checks all your boxes.
Review here with a subtle dig at woke.
https://rpggeek.com/thread/2495585/weaponry-attitude-and-grit-angsty-effetes-need-notThe full mammoth pdf is 25, you can get an intro or a sample version for free. Have a look at it.