Look pal, don't get worked up. I'll explain it to you more nicely why what you said wasn't ironic. You said:
There's nothing ironic about this statement. If you remove the word 'ironic' from this sentence, you are instead telling people how you first discovered Steam. There's no irony, situational irony or any form of irony here.
If you had, however, instead said:
"Ironically I bought a hard copy of a game to avoid using Steam, but it promptly told me that I needed a Steam account when installing."
That would be ironic. Because, in this situation, you ended up doing something you were trying to avoid in the first place.
Geddit now?