This is actually a stupidly niche question that I'm going to give a long answer to:
Whether or not you're good depends on your context. There are levels.
Level 1. I'm better than anyone else in my school, that I regularly play with, or I have a billiards table at my house so I'm pretty good -- Can sometimes go on 3-5 ball runs and usually does well in amateur tournaments at school or somewhere.
Level 2. I'm pretty good at the local pool hall, but I don't win or enter the tournaments - Can inconsistently run the table, but I don't feel confident to play for money other than maybe a $20 bet sometimes.
Level 3. I'm the best at my local pool hall, I regularly win/compete in tournaments for money, I play for hundreds of dollars regularly, I sometimes travel to play in bigger tournaments around me. I consistently can run the table.
Level 4. I am no longer allowed to enter my local tournaments except on special occasion, people will generally not play me for money anymore unless it's an incredible deal like a solid handicap + large wager. If you miss a shot, get comfortable, I will make sure you don't get a turn again. These are people who win scholarships, go on TV to play against celebrities, join national teams to compete internationally, etc.
The skill levels are generally separated by how often they miss, and the top tiers are separated by how well they can strategize.
Source: played pool once with my cousin