This is what literally makes tech workers go dream about farming.
When interviewing people, it’s usually possible to identify both extremes.
I’d prefer to hire someone who is not toxic. That goes for both extremes.
But what a person chooses to focus on does say something about how that person thinks.
If I ask someone what they dislike about their previous job, and they say something like "there were times when management would change directions at the last minute and cause the whole team to scramble", that's relatable and not necessarily a red flag.
If someone starts venting about low quality coworkers and shitty management, that's probably a red flag.
If someone volunteers negativity unprompted, that's probably a red flag.
My point here is that discerning between toxicity and honesty is usually possible, and what a person chooses to be negative about is a signal that helps tell the difference.
What I don't want on my team is a culture of negativity. A negative/pessimistic default is a wet blanket that shuts things down before they have a chance to get started. It creates tension where it need not exist. And it requires significant effort to counteract once it exists on the team. And to reiterate, I'm not looking for toxic positivity either. That's a separate problem.
I'm sure there are people out there who do have a toxic positivity problem, but my own anecdotal experience leads me to prefer to err on the side of rejecting unnecessarily grumpy people, because they tend to more frequently be a problem.
I think that may be a very cultural thing. I love gallows humor (I understand, enjoy, and cultivate it myself), but some cultures don't even understand it.
Maybe it works out in big orgs but if it infects the team of a small org your work environment will be ruined when you are all laid off after months or years of overworking to make a blind optimist happy. Unemployment coincident with burnout is worse than some negative feedback during the process.