It's a really "meh" appointment, but guess that's the feeling around the club in general. He's not being brought in to revolutionise what happens in the future after his time is up (unlike Ragnick's appointment which was supposedly made to accomplish), but IF there is a chance he can squeak us into that 4th spot then it's an incredible achievement for him. That's a big if...
As we have nothing to aim for except for some form of European qualification, with 4th place being the best outcome for this season, I had a quick look at the past 4 seasons for 4th place in the league:
24/25: 69 points
23/24: 68 points
22/23: 71 points
21/22: 71 points
We're on 32 points with 17 games remaining, which is a gap of roughly 38 points which could be a sweet spot to secure 4th comfortably. Granted, the teams around us playing for the same spot aren't exactly setting the world alight, but say that 70 is the average for 4th place then Carrick would need to look at winning more than half of those games, and keeping the defeats to 3 or 4 max.
If he can bring back the initial revival that Ole did as interim (which was wonderful for those who remember him for that and not the downfall), then he will have done a fantastic job as interim manager as well as giving enough time to sort out a full time replacement.
However, simply looking at the numbers above and the mentality of this squad currently, I feel he will be working through these final 17 games as a firefighter and we will fall short of a European finish come May :/.