Yeah, I was aware of the different armor types in SC1, but I thought they turned it up to 11 in SC2. Maybe they brought it down to the first 2 tiers of units? It didn't feel like armor types really came into play as early in the game. The impression I got was that you could get away with massing a single type of unit much more easily in SC1.
Yeah I've felt the same way at times, especially when the armor/weapon types make it very rock paper scissors. It wasn't as blatant in the original StarCraft, but WarCraft 3 and StarCraft 2 seemed to go hard into counters against certain types of units, so someone who either scouts a bit better than you do or picks an army composition that happens to perfectly counter yours will mop the floor with you.
My partner and I had way more fun in those early games when we could stretch it out to 30-60 minutes sometimes. Once you're playing against ranked people who are there to win it's just a mad rush to the first or second tech tier.
Back when I played it, there was a 50 game skill test for new players which determined which of the major rank pools you were placed in.
Those first 50 games were crazy because you were matched randomly with other new and established players, so sometimes you would play someone really good who would steamroll you in the first 5 minutes, and sometimes you got someone who had at most played the scripted campaigns against the AI and thought they could sit there for the first 30 minutes slowly building up an army.
It was actually pretty fun not knowing which way it would go, and whenever we matched with newbies my partner and I got to experiment with a bunch of different strategies that would never work in a real game.