I kinda liked the more comedic approach. The Ultra Guardian premise tended to be fun since, unlike most other antagonist plots in the show, it actually revolved A LOT around developing the dynamics of the heroes (or at least four of them, Mallow and Lana barely ever did anything in them). The Ultra Beasts didn't fight much but they had personalities and quirks that made them potentially dangerous, and I liked seeing the heroes interact and have to use eccentric tactics and craftiness for once to stop them. I think it also worked well to show more of Lillie and Sophocles' smart niche at times, since they offer strategies in several missions. These episodes definitely helped Lillie stay relevant in that post-AF lull where she wasn't getting much individual limelight.
I partially think this was due to story logic. With both Nihilego and Guzzlord they went for the more serious threat approach, but also seemed to acknowledge that the twerps alone couldn't realistically defeat them, so we got the usual formula of them trying but failing to battle until some DEM or outside interference makes it as easy as a button press. Doing this formula all the time, with the UGs constantly lucking out through plot armour would have been less interesting and also under repetition made them look pretty ineffective. The more light hearted face offs allowed way more agency to whole thing while also letting them add a variation of personalities to the other UBs.