There are plenty of positions where breaking even is fine. For example, a player on the Oilers' bottom half of the lineup it would be incredible to break even. For anyone against them, if whomever is matching up against the top guys going even is excelling in their job. What is considered doing a good job is context dependent on the situation. All that Blues team needed was average goaltending, and Binnington gave them average goaltending.
If you want to dive deeper, you can also look at the context of when the Expected vs Actual Goals happened and how a lot of the minuses were clumped in a few outliers, but we'll start with baby steps.
Yeah, for guys at the bottom of the lineup.
Your starting goaltender plays 60 minutes a game. There's no context where we can't compare him to a 1C or a 1D. He's arguably even more important in a vacuum.
There's no other position where you would look at dead even, and say that it's average. It's replacement level. It's significantly below average.
The biggest misconceptions with analytics are that 1) even is average and 2) replacement level is average.
Do such players exist in the NHL? Absolutely, because there's four line and three pairs. There's one goaltender.
You can bring up context and outliers, and just not agree with what the stat says, that's up to you. Objectively, a GSAx of 0 is terrible. It's just about sub-NHL. About 60 goaltenders are going to outperform that every year.