Hmm, interesting.
I do think Smash would still be a complete game, even if DLC (including Mewtwo) was never a thing, and I feel like that even if I didn't spit out extra money for Smash, I'd still feel satisfied with a finish product in my hands.
I think Sakurai is handling Smash DLC fine so far, and I'm hoping it continues to be great.
"Just for comparison Uncharted 4 was 20x bigger than Splatoon 2. This shows the huge difference between Sony's first-party games and Nintendo's first-party games."