Again, Time Traveling isn't the center piece of the Zamasu arc, he didnt go on his killing spree as a direct retaliation for Trunks helping out the heroes of the main timeline, shit prior to Trunks actually going back in time before Zamasu finished him off, he didn't even know they had technology capable of even achieving that.
Zamasu berating Trunks for his "sin" of time traveling was just him adding salt to the wounds trying to "gaslight" him into believing that everything was his fault, typical villain shit talk tactic.
Vegeta and Freeza were destroying and conquering planets waaay before they even knew the Dragon Balls even existed, hell Nappa initially only wanted to invade the Earth to avenge Raditz and potentially revive him until Vegeta mentioned immortality. On top of that they only even LEARNED of them because the scouters are galatic walkie talkies. If Bulma hadn't created the radar, eventually Pilaf or Commander Red would've gotten to the DBs and had their way with them. As stated before the Dragon Balls are a neutral plot device, the crux of most of the stories they're involved in is that any person good or bad can get a hold of them its just a matter of who gets them first. Same thing with time travelling, technically with the new rules its "forbidden" but anybody can do it with either good or bad intentions and the repercussions if any (there havent been any) will vary.
Saying the Dragon Balls should only be used for noble causes is you making up your own rules, you dont have to like GTs added limitation of them needing at least 100 years to fully expel the negative charge thats created within them when A LOT of positive energy was used grant a wish like reviving billions but it doesnt contradict anything that's pre-established. Lets also keep in mind that the Dragons were also upgraded several times as well so its not like there's all take with no give with what they're capable of doing.
The Shadows Arc is the only time we've seen a DIRECT CAUSE AND EFFECT of the overuse of the Dragon Balls. Whether you like it or not is totally up to you but it doesn't change what is.
Outside of GT we've yet to see any consequences for either over using the Dragon Balls or traveling through time be it for good or bad reasons. Merged Zamasu becoming grotesque was a by product of him underestimating the heroes and the potential draw backs of combining an immortal body with a killable one. The Super DBs did their part already by granting the wish, what the Zamasus did after getting their wishes granted was completely on them.
I think i've added all that I could to this particular part of the conversation, You can respond if you want but I'm starting to feel like we're gonna be talking in circles sooner rather than later if we haven't already.