There is so much in baseball that is random, so it can be misleading to gauge performance based mostly on a few metrics without context. A really important piece of context is the strength of opposition.
For example, my 12-year-old son was on a medium strength AA team this summer that improved to become a strong AA team by the end of the summer. But occasionally we played against much stronger AAA teams, and they would easily beat us with a mercy rule kicking in after 4 or 5 innings.
Normally, AAA hitters would have their way with our pitchers. My son (also a lefty) was one of the better performing pitchers on the team in general. One time against a AAA team he did terrifically, because he had everything working for him that day - his control, his secondary pitches, etc. as well as his pitching smarts. So . . .
He noticed that most players on the AAA team stood far from the plate. So he'd throw the first pitch to barely catch the outside corner. Second pitch the batter would scoot closer to the plate. So he'd throw high and inside for a strike. And he mixed in his football curve here and there.
He issued no walks. Did they hit him? Yes they did. In 2 innings of work they hit maybe 5 or 6 balls into play, only one of which was a solid line drive, the rest of which were fieldable. His teammates made a lot of errors behind him and a few runs scored, but that didn't affect his pitching (not being bothered by the errors behind him was another reason I thought the outing was a great success).
These 2 innings of pitching were arguably his best 2 innings of pitching this summer but you wouldn't know it from the stat line. The context of playing against a really great team (that won every game at the tournament, mostly by mercy rule) and having fielders not do much for him that day made the stats look bad, but his control, command, composure, and smarts were all very much in evidence.
Over time, the stats become meaningful as some of the random elements and contexts average out. So after 25 or 30 innings, those things like K/BB ratio, WHIP, etc. will end up reflecting performance. But for any given inning or even any given weekend, you don't want to evaluate performance purely based on stats.