And, you're conflating enthusiasm to continue playing (at all) with enthusiasm to continue playing (the character just deceased).
No, he isn't. Not even slightly.
You're making a huge and bizarre assumption that the group in general will be excited about having essentially wasted several hours creating PCs who are all now dead, and doing an adventure that they definitely aren't going to finish. Doesn't make sense.
Hot take: players who give up like that just because they lose a character or three probably aren't worth keeping.
That's not just a "hot take", that's judgmental in quite a knee-jerk way,
flatly insulting to a lot of people here reading it, and shows an apparent serious lack of broad experience of different players/groups/games on your part.
Why's that? Because if that's how they think, it's a huge red flag that if-when things go sour for their characters in the future, it's going to be a headache. I've had players like that; the key word there being the past-tense "had".
You're showing what looks very much like a lack of real/broad experience here, presumably because you're quickly pushing people out of your group if they don't respond super-positively having their PCs killed. You pretty much directly say that with "had". You're selecting hard for players who love to die, which is preventing you from seeing players who don't, but are also good players - instead you're only left with people who hate dying, but who think "bad RPG sessions are better than no RPG sessions", which is not great, and who generally aren't a lot of fun to play with.
You're also conflating setbacks, and your losing your PC and all the emotional investment, actual effort involved in creating them and so on, and that's flatly nonsensical. It's just not the same thing. In reality, many players who love their PCs, love setbacks. To the point where entire games basically use this as a major mechanic - Chronicles of Darkness (i.e. the nWoD) is essentially designed around this - the chances of losing your character without something wild happening are close to nil (not like Russian Roulette like some OSRs or early D&D). The chances of setbacks? Basically 100%, and some of them are going to be absolute whoppers.
If players operated like you say, neither the oWoD, nor the nWoD would have been at all successful, nor would many other RPGs. But they were successful, which frankly, immediately disproves your theory.
Even on a more straightforward level, a lot of players who care about their characters will to huge lengths to keep going - they won't get upset by "setbacks" - on the contrary, those motivate them to find ways around them so they can keep playing their character and keep their character alive.
There are players who give up at setbacks or get excessively upset by them - they're usually just people aren't having any fun generally - usually due to a DM/player, game/player or player/group mismatch*. If you see players giving up, and you immediately paint "BAD PEOPLE" or "BAD PLAYERS" on them, as you're claiming you do, without thinking more carefully about the causes, well, that's your choice, but it doesn't mean you're right. My experience is that if people are giving up at just setbacks, you probably need to change something up.
That can mean that the player is just not going to be a good fit, sure. It does not mean they are a bad person (all the worst people I've ever played with weren't giver-uppers, they were game-wreckers). But it can also mean that maybe that adventure is really boring. Maybe this game system isn't really working out. Maybe this person is generally unhappy with their character.
I mean the latter is surprisingly common in my experience - I had one of my players is the main group who was really having problems with setbacks the party was facing, and just seemed frustrated, and we talked - and figured out he should play a different character for a while, and then he had a great time (and even eventually went back to the first character!).
* = There is another group which is "literally children" (including teenagers) who it's very much down to a personality/emotional development/home life/hormones and so on. Kids who couldn't handle a PC dying on a Tuesday might well be able to on Tuesday next week because they're in a different mood etc. but I'm largely excluding them because that's whole other discussion.