Incremental games are a bit of an “I know it when I see it” grouping, but two typical characteristics are progression systems nested within each other and game loops that start simple but “flower” into a number of more detailed and mutually interacting ones over the course of play.
Universal Paperclips is a nice example, casting you as a newly built AI with the goal of making as many paperclips as you can. You start out able to make paperclips and sell them to humans for funds you can then use to invest in more capabilities. You work on building trust with the humans so they’ll let you do more things, and on making more clips faster, and there is a lot of escalation from these humble beginnings. Some other good ones are Cookie Clicker and, if you’re into programming puzzles, Bitburner.

This is definitely important in making the very most engaging base-builders - a pleasing mixture of longer term goals (manufacture this piece that I can eventually put in a future science pack or whatnot) and under-performing pieces of your older infrastructure that you have to scale up or re-plan is just so helpful for getting you into that flow state.