I do agree with you about Tekken having simple and natural combos but learning characters in Smash is, imo, 1000x easier than learning characters in Tekken. Even without giving you tutorials on how to play individual characters, it's not that hard to learn a character's entire moveset. There's only a few moves which would really trip up someone new to the game, such as what Rest does or recovering with PK Thunder. A big difference there, however, is learning how to do it can be done from watching others. You could easily figure out which move it is just by testing the character and finding which button and direction to press. Can you do that in Tekken? Not really, you have no idea what inputs were used for moves that aren't just basic punches, kicks or throws. Then if you want to learn combos, it's still 80+ options to choose for each move, which extend beyond a button and a direction. Now with experience, you'll know which ones to use and when but it's still 80+ options to choose from.
Not necessarily, since learning to play a character competitively in Smash entails knowing the exact percent value at which combos work and being able to get your opponents to that percent value to execute your clutch combo, which you do by knowing exactly how much damage each attack does. You also have to be half decent at platforming type gameplay. You also have to learn the weird nuances the different characters have, like Shulk's Monado Arts, Rosalina's Luma and how she controls it, Ryu and Bayonetta's unique controls, Sonic's Spin Dash, Marth's tipper, etc.
Through reading the responses here, it seems people aren't sure on whether we're talking a competitive context or a casual one. I was talking a casual one before because not many people here even play in tournaments so they can't say they are competitive players.
In a casual context, Tekken is one of the easiest fighting games to pick up and play. Two punch and kick buttons isn't hard to learn at all and clicks immediately. And people will naturally try pressing buttons at the same time or pressing different buttons in combination with each other (i.e. button mashing), and notice the different results. Most people I know do this before ever checking the move list, as it's a better way of learning characters.
Pokken, by contrast, has a lot of arbitrary mechanics that aren't intuitive. For starters, it has two gameplay systems you have to learn, heavily inspired by two completely different, existing games (Duel Phase is Street Fighter, Field Phase is Naruto Ultimate Ninja Storm). Then it has the arbitrary conditions of what triggers a Phase Shift (which I never fully grasped - I know grabs cause it but it doesn't make sense to me why they would, and I know it can be caused by other means but I've never understood them). There's also the fact that the two different phases are different even dimensionally - one is 2D, one is 3D, and as such, you have to remember the arbitrary differences that come with that. In Duel Phase, Pikachu can't just sidestep an incoming attack because I don't know. But he can in Field Phase. Again, it's arbitrary. Both phases have completely different control schemes too. In essence, learning a single Pokken character is actually learning how to play two completely different characters from two completely different games. And I do mean that literally, because like I said, both of Pokken's gameplay phases are ripped from different games that play totally differently.
I also don't like Duel Phase very much period. It's just a dumbed down Street Fighter, and I don't even like actual Street Fighter that much (which is purely personal taste, I don't think it's a bad game or anything). And it baffles me that the developers designed Pokken around two completely different gameplay styles, as if to assume everyone would like both. Sure, if it was just Field Phase but more fleshed out, it wouldn't be an actual competitive game, but it's Pokemon, it doesn't need to be.