What do digimon look like?
"Pointless" markings oh nooo
Armor, seriously?
I have no idea what kind of complexity in designs you are talking about.
Ivysaur is based off of dinosaurs and lizards in general, which have those markings.
With Nidorino, you have a bit more of a point there, but still, it isn't very complicated at all. Plus, the markings blend in and don't stick out to "decorate" the Pokemon.
Vileplume is based off of the vile-smelling
Rafflesia flower, which has spotted red petals. The markings are completely justified.
Parasect's mushroom is based off of real-world mushrooms, especially the toxic
Amanita Muscaria, or Fly Agaric. Fly Agarics have spotted caps. Again, the spots on the cap are there for a good reason, unlike the new Pokemon.
Kadabra's multicolored, segmented body is intended to make it look mystical and alien.
Marowak's skull helmet draws inspiration from the ancient Samurai warriors, and it ties into the whole backstory of Cubone and Marowak.
Kabutops is based off of ancient crustaceans and the whole concept of fossils, with it's segmented, rocky body; and similarly to Marowak, it contains similarities to warriors, with it's blades and armor.
Donphan doesn't really have armor. It's trunk covering is based off of a truck tire, which explains how it can curl up and roll over enemies.
Your argument is invalid. All of these Pokemon have simple-but-good designs, and sure, they might have been some of the more complicated-looking Pokemon of the time, but their armored appearances and markings were justified. Unlike newer Pokemon, which have armor, spikes, and markings thrown on them just to look "cool" to the kids
(And that's exactly what I mean with the Digimon comparison, Digimon have pointless armor, spikes, and markings), the older Pokemon all have reasons for their armored bodies and appearances. And you can sure see a difference in complication when you compare the old Pokemon to, say, THIS thing:
See what I mean? With Haxorus, GF took a basic fantasy creature, a dragon, added pointless armor, some pointless tusks that aren't really based off of anything, some spikes just to make the kids happy, and they called it a Pokemon. Note that this thing is so overcomplicated that it would probably be a Legendary in any Generation before IV. Yes, it is even too overcomplicated for Gen III.
Compare Haxorus to another, much older, Pokemon based off of dragons:
That's right, the old favorite, Charizard! With this great Pokemon, GF took a dragon and flawlessly incorporated it with the element of Fire, adding a flaming tail and a fiery red color scheme.
But before you call me out for "Hating Gen. V", take a look at my username:
Elgyem. Elgyem is pretty simple, aside from the lines on it's head (which don't really add or detract from the overall appearance of the Pokemon), and it has a clear origin:
Alien Greys.
One more thing about Generation V that I have to say: Fire/Fighting starter AGAIN? SERIOUSLY?
And as I said, Generation V was mostly an improvement over the putrid Generation IV.