I really have no idea what Foster has been trying to achieve. He hasn't made decisions about who his core players are, he has just seemed to roll the dice each week. The only players you could call reasonable certainties to start are Whitelock, Rettalick, Savea, Cane, Smith and Jordie Barrett. None of those players have been introduced since the last world cup and only Rieko and Akira Ioane and Jordie Barrett have made significant progress since the last world cup. The rest have largely muddled along.
I think that's probably a tough assessment of what's been happening. I don't really think that many players have laid claim to jerseys the way AB's of the prior generation did. I think he has been changing it up because they aren't getting the results from players consistently. A good example is that Havilli had a few of really excellent outings but then struggled to impose himself physically. I think Akira for example had a great end to the previous season, but then wasn't as good the following one (but still a considerably improvement over the seasons prior at any level). Compare that to Kaino, where he would have been the obvious choice week in and week out for a couple of years at least. Nonu and Smith who were the only choices unless not available. There aren't that many players right now that are total shoe in for a position or jersey.
We have also had a massive number of key players injured or unavailable. I think that makes it pretty hard to build a good team structure and get consistency. A number of times, players were played because they were pretty much last man standing.
Where the AB's have done well in the past was introducing players into an experienced team, and with a few notable examples, we have seen those players step up and become test level players. I don't think that has been as obvious for the last little while. It could be poor coaching, though to be fair to Foster, with some bad has also come some pretty decent results too. We were the best Southern Hemisphere team last year by a decent margin.