The "backs against the wall" and "underdog" Celtics are fun to watch and usually do very well.
My worry though is, if there's something going on behind the scenes. Maybe some locker room tension, or tension about the future Celtics ownership sale, or even just feeling like they aren't at the level of OKC/CLE.
I think the best "hope" is they are truly coasting and just going through the motions since it's still January in the regular season with the All-Star Break and 2nd half still to come. Not making excuses for them if true, but at least then they could have a shot to figure it out and play better when it matters.
If it's not though and it's the first thing (a lot of tension or locker room issues or a combination of both) then that'll be a problem that unfortunately doesn't go away and might even lead to an exit before the ECF.
I also have wondered if it's one of those weird things where everyone is healthy (including Porzingis) and they just aren't used to it. I mean Porzingis is usually hurt and they got used to rotations and playing without him. Now everyone is healthy, and maybe they are still building chemistry with everyone and figuring out rotations better.