@PhilJax ... Couple reasons. Firstly this is the best league in Australia, so naturally it's going to be the most competitive and toughest, you gotta give it credit. But looking at your team and how you do in games ... I notice you have a very high salary starting 5, but not a lot of backup after that. That can be a successful strategy (most top B3 teams I've seen seem to do that) but that's based around very high stamina and heavy minutes for those salary beasts (and I don't know for certain, but I'm guessing a fair bit of GS training).
But your biggest problem is a surprisingly low amount of OD, your perimeter defence ratings are not as high as they should be. And with OD being the best skill in the game, I'm guessing that's costing you.
That's just from a quick look at your team through the team stats page of buzzer-manager, beyond that you'd need more specific questions and to offer more detail for a more specific answer.
For an example from my own past teams, I once had a SG with about 120k salary who was a scoring beast, I think he might have come second in the MVP vote one season when I made it to the ABBL finals. However his big downside was only having 15 OD ... 15 is far too low for someone defending the 1, 2 or 3 in this league (well maybe 3, matchup depending ... But you'd also need great ID too).