Please note that in this post, as in all of these, I’m using the words toy and game as previously defined under my own opinion, and the words are used only for clarity, not judgment. A game is not by any reasonable definition necessarily better or more fun than a toy.
a game doesn’t need an objective just interactivity.
You’re describing a toy or artpiece, not a game. Games need both. A physics sandbox like Garry’s Mod is a toy. Using it to play Hide and Seek or something is treating a toy as a game.
not sure why you mentioned outer wilds
Because you brought up playing with games (treating them as a toy) rather than going after the objectives laid out for you (treating them as the games they are). Trying to repair my smashed-up spaceship mid-flight has little to no relation to the objectives of that game. Neither does seeing how hard I can smash into the ground and launch the cockpit from the main body, or trying to achieve a stable orbit around a planet or the sun. That’s just treating it as a toy. And if a physics playground was all it was, it might still be fun to play with, but it wouldn’t be a game. (Conversely, if you couldn’t do these things—if you couldn’t take a break and treat it as a toy—it might not have been as fun of a game.)
you can just ignore the score and the game doesn’t change
You could, yes. Just like you can ignore the mystery in Outer Wilds and spend the whole time messing about in its physics sandbox. But that’s treating a game as a toy. Or treating the game as a toy that you’re treating as another game in which you fly off into space and see how high you can push your speed before the sun goes nova. Doesn’t change the fact the actual game still has its own objectives.
And if you’re not trying to beat your own high scores in an arcade game or shoot-em-up or speed-runner where score-chasing is the whole point, you’re not playing the game. You’re playing with the game like a toy. (And that’s frankly what I tend to do with score-focused games.)
[In Superflight] there is a Zen mode with no scoring system, in this mode dying […] sets you back to the beginning of the stage
I had to look this up and the video I found appears to contradict this, or maybe it’s a different version. Anyway, I mentioned “surviving as long as you can” as an objective to distinguish it from simply “not dying”; if the game tracks that you made it to level 19 or dodged 114 bullets before dying on your best run, that’s a high score, that’s an objective. If it doesn’t, it’s not and there may not be one.
TL;DR: If you don’t play a game “as intended,” you’re treating it as a toy. If you can’t tell how to play it “as intended,” it’s not a game. Either might be fun and either might be boring.