Deep Rock Galactic 4/5
You and three dwarf friends drill deep into an alien planet in search for exotic metals and stones in a futuristic setting. The game plays a lot like vermentide, with 4 unique classes which synergize very well with each other. The maps are proceduraly generated (therefore they are always random). The enemies are bug like creatures that crawl all over cavern walls. The entire environment is destructible and the game gets progressively harder as you level up. Awesome environmental effects such as earthquakes causing massive fissures to open under your feet. A match takes about 20 minutes or so to complete the objective and get out.
Its pretty cheap, maybe $15, still in Alpha, but we have only experienced 1 glitch (for some reason you cannot map any keys to "p", no clue why). The graphics are simple and cartoonish, but still look great, the code appears to be pretty optimized so your old machine can probably handle it.
Bonus: it has THE BEST ready room I have ever seen in any game, by a long shot.
Downsides: The range of upgrades seems fairly limited, but that is likely due to the game development still in alpha. Most missions are a "resource collection and get out" which becomes a bit repetitive, thought with the changing environments, it always feels a bit like a whole new experience every round you play.