Yeah if someone is struggling to pass the ball, then by all means, keep the serve on 'em. In beach vball sometimes you can serve the weaker hitter or passer from the other team into a rhythm, actually helping them. That probably applies sometimes indoor as well. If they're passing the ball well, there's no point beating your head against the wall. Gotta be willing to change shit up if needed. As a player, I had a decent topspin jumpserve, but I got a ton of mileage out of changing shit up all the time, like a baseball pitcher. I did everything. Topspin jumper, standing topspin, cut serves, floater, varying pace, short/deep, serving from all across the serving line, serving from way off the line or right on it, crosscourt/down the line/up the middle, etc, etc. Anything to keep the other team from settling into a rhythm. And more often than not, that worked. I didn't see this match, but I've noticed we don't seem to have much variation in our serving.
Semi-related csb: Once in the firefighter olympics state bvb tournament, we had this guy on the other team in the tank. It was July. Old rules, big court, sideout scoring. Grinding. He was hot, and he was fucked. We were cruising. We had gone undefeated in pool play, and this was like the third round of single elim. All we had to do was keep it on this guy, and we were through to the semis. My partner Alan knew the guy, and started feeling bad for him. He started serving the other guy instead, giving his friend a break and ltting him get into a rhythm setting for his partner, who was fresher and was a better hitter than him anyway. Crazy. Kept doing it. They ended up coming back to beat us like 18-16 or some shit. Fuck Alan. Never played with him again. Dipshit motherfucker. Wasted my fucking Saturday. /rant