The information how to counter things is fairly intuitive and/or easy to find, though.
I mean, I played a little during the very first stress test weekend and I've only had one night to play in the current early access thing so far, and I'm pretty familiar with the heroes, maps, counters, and so on. There's not some gigantic amount of knowledge that you have to amass to be proficient.
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It's not like Junkrat bombs are invisible or even silent. You're not "just happening" to bump into one, you just weren't paying attention. And if you cornered yourself against a Junkrat player in a little room or something? Well, you goofed up.
And yeah, a grenade in CS:GO is going to do the same thing to you if you're at low HP and camping in a corner that everyone knows you're camping in. You'll "just happen" to get hit by an "RNG" grenade.