Baseball has a lot of scoring rules that don’t make sense, really, but wins is the one that makes the least sense.
If wins and losses are an inaccurate indicator of how good a pitcher is, what are some examples of good pitchers with lousy W-L records and lousy pitchers with good W-L records?
For the first example, Nolan Ryan went 8-16 in 1987 while pitching to a 2.76 ERA and 270 strikeouts, in an extreme pitcher’s park.
Outright bad pitchers with good win totals are rare, because if a pitcher can’t get three outs to end an inning there’s no way to keep the offense from scoring at will. The mediocre will often have a high win season thanks to good support. Steve Stone won 25 games (and the Cy) in 1980 with an ERA of 3.23. MLB average that year was 4.29 so good but not amazingly so. His Cy rival had 2.53 with more strikeouts and innings pitched. Stone’s relievers blew no saves in his wins.
In 2006, Randy Johnson had an ERA of 5.00, which was the worst of his 20+ year career. Yet he had a W-L record of 17-11.
Stone is a classic example of a solid, but unspectacular, player who has one season where he catches lightning in a bottle, and has no small measure of luck during that season. He had a good, but not great, ERA in '80, and his WHIP was a fairly pedestrian 1.297 (not that many people had even heard of the WHIP stat back then).
Take 1980 out of his career stats, and he has a record of 82-86 (mostly playing for the mediocre Cubs and White Sox), a 4.09 ERA, and a WHIP of 1.364.
Two years later, the AL Cy Young went to the Brewers’ Pete Vuckovich, who was likely even less deserving of it than Stone was. Vuke went 18-6, for a team that won 95 games and the AL pennant, but with an ERA of 3.34, and a fairly ugly WHIP of 1.502. I’m fairly sure that it was the gaudy win-loss record, and playing for the Brewers’ first (and, to date, only) pennant winner, that did it.
Edit: looking at Baseball Reference’s WAR (wins over replacement) ratings, Stone had a 4.0 WAR in '80 – good, but not exceptional, and Mike Norris, who finished in second place for that Cy Young, had a 5.9 WAR. Vuckovich had only a 2.8 WAR in '82, which may be the worst WAR for a Cy Young winner who was a starter, and pitched in a full 162-game season, at least in the expansion era.
Nolan Ryan in 1987 has been mentioned already. The same year, Orel Hershiser was 16-16, which looks mediocre but he was one of the best pitchers in the league. After going 23-6 in 1988, he went 15-15 in 1989, but again he was one of the best pitchers in the league. In 1991, Greg Swindell went 9-16 but actually pitched really well. This sort of thing happens all the time, really.
The career champ is Bobo Newsom, a pitcher back in the 1930s and 1940s who was pretty good but managed to be the only pitcher to ever win more than 200 games but have a losing record; he was 211-222. In 1945 he pitched pretty well but went 8-20; his team was far and away the lowest scoring team in the league. Most of his career he was on crap teams.