Win rate tells you only how often you win. To understand the economic structure of a strategy you also need to know how much you make on an average winner and how much you lose on an average loser.
Why the conclusion can change
A strategy with a 70% win rate can still lose money if average winners are 0.3R and average losers are 1.5R. Another with a 40% win rate can be positive when its winners are much larger than its losses.
Relationship with expectancy
Expectancy combines probability of winning, average win, probability of losing and average loss. These metrics belong together rather than in isolated scorecards.
Watch for outliers
One or two exceptional winners can inflate the average win. Compare median, distribution and trade count as well when those data are available.
What it can reveal about management
A declining average win can point to exits that are too early, aggressive partials or fear of giving back profit. A rising average loss may indicate moved stops, slippage or rule breaks.
Compare by strategy
Do not mix systems with very different profiles when trying to understand the cause. A scalping strategy and a swing strategy can have very different win/loss relationships and both be viable.