Yeah, it's definitely not got that bright, optimistic vibe he has in his fun-for-the-whole-family flicks, and I wouldn't write it off either despite its huge missteps near the end, but I do think there's a point to be made that even in his harder stuff he can't seem forgo a happy ending as he's gotten older.I know what they meant, but nothing about War of the Worlds seemed like "gentle Dad Spielberg."
Plus the reason that ending fails isn't because the kid lives, it's that a key emotional moment in the film was already struck through the notion that the kid died, that we saw it happen, that Ray moved on from it (kind of). It wasn't just Spielberg refusing to kill a kid at the end, it was him basically undoing a part of his own story for the sake of the happy ending. Which is a problem of his (and has been, yeah) but even him fucking that up like he did isn't enough to make me come anywhere close to writing off the movie.
Heck, the initial alien reveal / attack at the beginning is one of the most intense, well-shot things Spielberg has done. Which is what makes the flaws later on more glaring for me because of just how good WotW is aside from them.