Oh I'm sure it's deeper than I every thought it was. Tekken 1 was my first Playstation 1 game and I've played every game since, so maybe growing up with it feels easier. However i am no combo master nor do I really know the moves with any given character.Tekken is actually a lot more complex than it seems, you have to learn to do the korean backdash for example, and people complain about that and about juggles day and night. Also chars have a million moves so that's just more complex in general, though you can do fine with only using a few of the good ones.
The reason tekken feels easy is that you have really high damage and the attacks are more often than not straightforward enough, so you can kinda get the feel of the flow and no matter what you do you are gonna get similar results, only something like Lei's animal stances or Yoshimitsu stabbing himself or meditating at the wrong moment can really screw you up. At a low level you have very few things to keep in mind.
Though it always had a lot of silly stuff, it had demons shooting lasers and ogre breathing fire and the panda farting on you. Now they just added some more chars who have those like the robot girl with the chainsaw arms but you can still just use the 50 or so other chars who are more standard too.
But Tekken does let me think like a real world fighter. I don't need crazy juggles, I don't need flashy lasers, I just need to bob and weave and strike when there is an opening. It makes more sense to me for whatever reason.
Meanwhile a game like Mortal Kombat requires me to know the fundamentals of each character. Knowing Sub-zero's ice throw, or Scorpion's "get over here" and teleport. You literally can't make it through matches without knowing those things with each character. Whereas in Tekken, if you can time punches and kicks you can get by well enough with low to average players. At least it feels that way.
I tried Dragonball Z fighters and damn near lost my fucking mind. The combo's, beams, chracter swapping, team building synergies,.......fuck it my brain explodes.