KAT was starting. Kyle Anderson was signing. Kessler was drafted. Naz Reid had completed his 3rd year (was a rotational BIG for 2 seasons at that point).
Yes, KAT was starting at center and it was disastrous defensively.
Kyle Anderson is a fine basketball player but not anybody that should be starting or playing more than 20 minutes unless against particular matchups.
Kessler was drafted at #22 and not expected to make such an impact.
Naz had completed his 3rd season and was indeed a rotation guy.
None of those 4 guys were expected to be able to compete defensively against the best of the best (Jokic). Maybe Kessler could have done that, but a rookie #22 pick is not expected to do much.
They got some stuff wrong for sure, and way overpaid (way way overpaid) and maybe a Kessler/KAT/Naz front line with a different PG with the assets sent to UTA would make them a better team, but that seems unlikely considering they are in the conference finals and just beat the defending champs.