They definately have great ability. But both players are far from consistent. If there were an award for "Most underperforming player of the past decade" Webb would be in the top three. Maitua himself is quite inconsistent. He performed in a supporting role behind the greatest forward back of the past decade, but he was cold more often than hot in his last couple of years at the Dogs. So yes those two blokes have the ability, but they're also lazy and go MIA a lot of the time.
Shacks is a bloke who puts 100% in no matter what, which is equally if not more important to a football side than natural talent. That's why the club signed him because he has ability as well as doing the hard yards and were really impressed with his attitude. Ability only does so much, it's hard work that makes the difference in the end. And in regards to Maitua's fitness, there is a difference between general fitness and football fitness. It's all well and good he's kept himself fit, but he won't have taken part in any training drills and ball work for 2 years and won't until May. Wendell Sailor made his comeback in May too, but it took him until the end of the season after 2 years out to get a regular crack in first grade. And he was just winger, and a far better player than Maitua.
I'm just being realistic. Webb and Maitua have not been players that perform on a week to week basis for a long time now. Hence why their previous clubs let them go so easily. So we shouldn't be expecting too much of them.