Those guys aren't really awful players (Chappell and Groves definitely struggled), but we've needed to get strong imports in most cases and so the picks have been underdone.
Been discussed a few times on here before but I'm not sure if you've already seen those threads. Guess it'd be a mixture of stronger competition from other leagues as well as a greater focus on Australian talent and a preference for known quantities. Plus maybe honing of what shapes a successful team here these days.
I think many teams would rather have someone they know will be used to the league, the refs and the expectations. e.g., a Gibson over an import PG who might be the next Wilson or Jackson but will more likely be Groves, Shannon, Warren, etc. Easier to plan your machine when you know what you'll get from each component. Also, a solid but not brilliant local (think Gibson rather than Newley) is easier to keep around for stability/etc. So teams prioritise their Australian pieces and then often have less money spare for imports; some import salaries around the league are really not high at all. Last year, both Hawks imports would've been very cheap, both Blaze imports were cheap, at least one Kings import would've been budget and so on.
One thing that should've been working for us (and maybe has been a bit) is the Australian dollar. Imagine if things were as they are but with our spending power at 60-70%.