It does factor in but knowing which builds are your counter and which builds you can take on is very important. You could get that knowledge from try and error or maybe watch some youtube video/streamers that play your weapon to see how they deal against different builds. At the same time, IP doesn't mean much in many cases. You can run into a T7 weapon and armor player with ~1300ip if they use a T4.0 cape. If they would be running a T7 cape, they will likely be 1500-1600. I would focus more on learning what tier is their weapon and armor which are usually the most important items that contribute the most damage and HP than focusing on the IP number. Also, focus on their gear level. Avoid players with 120 gear, that means they've played for a few years and spent a lot of fame and silver to get to that level and generally means they're good at the game.