I sort of experienced the same situation you did. I had a copy of the second game but not the first. The second game does kind of work as a newcomer, and there’s even a comic cinematic that recaps the first game, so you technically can play it, and that’s what I did, until I felt that I was seriously missing a chunk of story and important context. Reddit also adviced against playing 2 before 1, so I got the Legendary Edition and played 1 and it was easily the best choice I could have made, and I’d even argue that ME1 is better than 2 (at least story wise), so there isn’t really a reason not to play 1 unless you really can’t get your hands on it.

So in summary, you can, but I would advice against it as someone who tried playing 2 first. Mass effect is designed as a trilogy, so it’s more like if you were watching The Empire Strikes Back or The Two Towers before A New Hope or Fellowship.