The phrase "linear progression" means that something is moving or developing in a straight line, step by step, without any major deviations or changes in direction. Full definition
Another key difference in a construction resume is that many careers in the field comprise a variety of projects, not a smooth, linear progression from job to job. (theladders.com)
As for the open world feel to things, and well, some will hate it and long for a more linear progression system, whilst their friends might just love everything about it. (thexboxhub.com)
It's a very linear progression system, and one that I didn't find particularly compelling. (cheatcc.com)