Some of these may fit the bill (when it comes to "mood" or "vibe"), while some are borderline cases. Some have already been mentioned in prior posts.
- 3-D Tic-Tac-Toe
- 2048
- Adventure
- Atarowg
- Backgammon
- Checkers
- Codebreaker
- Computer Chess
- Concentration
- Crypts of Chaos
- Dark Keep
- Dice Puzzle
- Dungeon
- Encaved
- Four-Play
- Kuru Kuru Tsuchinoko
- Moth
- Othello
- Raiders of the Lost Ark
- Raster Fahndung
- Riddle of the Sphinx
- Stellar Track
- Video Checkers
This list is not exhaustive. As for the "sim" or "civ" type of game, I don't know of any 2600 title that approaches that concept. Stellar Track (a GREAT game!) might come the closest.
For slow-pace and for strategy, my recommendations are 3-D Tic-Tac-Toe, Adventure, Crypts of Chaos, Dungeon, Riddle of the Sphinx and Stellar Track.
Yes, read the manuals! Atari 2600 games are often more intricate and nuanced than they seem at first, and many folks give up on games not realizing there is more meat on the bone. 2600 titles just usually aren't self-teaching in the way we became accustomed to from NES onward.