Am I doing something wrong?

So I'm a fairly new player, and I've been trying to get into the game, currently SHD lvl 45.

Am I doing something wrong?

In the beginning to level 40, I could feel tangible increases in progression obviously because the loot was consistently better. I got the advice to play countdown on challenger, but I mostly dont contribute much even if I can do summits on challenging/heroic with heartbreaker.

I also dont really feel like the loot I'm getting is that much better, even if I target what I want to try and create a build.

Not trying to hate on the game, rather just trying to get into it, but as of now it feels kinda slow and I dont really know what to do, even with all the advice thats been given to me