I don't think Barrett is anywhere near Keenan or Ringrose, but that is bye the bye.
In general the evidence against high profile kiwis coming to Europe at the end of their careers is pretty damning, most seem to treat it as merely topping up their pension fund with the exception of Brad Thorne, and yes I include Dougie Howlett in that, for who he was and what he contributed to Munster I thought he was a disappointment.
Look at the 3 best signings from there that Ireland have had, Bundee, Gibson Park and Lowe, none of them All blacks, the residency rule gave them an incentive and they've performed accordingly the rest have been meh in my opinion, and I don't think Barrett will do anything to break that trend.
You can see the logic behind the central contracts but with Leinster dominating the Irish set it is time to change it and maybe give each province a similar amount but ring fence some funds for whichever province supplies the bulk of players to Ireland so they can expand their squad to compensate for when these players are in the Irish set-up, but stipulate these extra squad members are Irish as opposed to beefing up with extra foreign players.
Currently with the way it is, the obvious thing for Munster and indeed Ulster is to pump more funds into underage at possible the expense the senior squad as if and when these players develop Munster will reap the benefits not just the obvious in having better players but also increased funding if they go on to play for Ireland. It is not beyond the realms of possibility as in the early noughties Munster schools regularly beat their Leinster counterparts and that fed through to the senior team where we dominated Irish squads.