So, the main reason 3D shooters are beneficial is because it forces you to solve complex problems at a fast pace, so any games that meet that requirement will probably give you the similar benefits. As a Mac user, a great starting point would be to just download Steam and explore the store to see what games get your attention. There are lots of lists from both Steam and user curators about awesome games, and they can generally be had for pretty cheap, especially indie games.
If you want one specific game, I'm playing Shovel Knight right now, and absolutely loving it. It's a twitchy and tough platformer that will definitely give you a mental workout. Their three-game bundle is available for only $19.99 right now.
Hollow Knight is another metroid-vania-style platformer that has won several awards this year, and it's on sale for less than ten bucks.
If you're looking for something different, Don't Starve is a game from the survival genre that will keep your brain going as you try to gather and manage resources. It's somewhat slower paced, with less emphasis on the action, but it's difficult and engaging, and the Don't Starve mega-pack with several games is on sale for under $13
There is a sale going on right now, so there are lots of great, cheap options. Check around and see what tickles your fancy!