Okay, let me reframe the "taco truck" to something else. Cosplay.
You make a costume, make it the best to your abilities and go out to see the reaction of people seeing your costume. Fine. But here comes another person who has done the exact SAME character as you did.
My reaction as an outsider and taking the picture is "Wow! More of my favorite character", while one of the cosplayers is mentally biting their thumb thinking "how dare the other person cosplaying this character is stealing my thunder". JFC, to that person in my example, get over yourself. The other person is just getting angry over the fact the other person DARED to do the same thing. If this is enough to cause that person to lose "motivation", then the reasons for being there were pretty weak to begin with.
Cosplay isn't a 1 to 1 comparison either.
Cosplay as a hobby is more of a show of appreciation of a character and the like.
But translating is more of presenting a product in a way. You can't really bond over selling a similar product like you can with cosplay.
You put your hours into translating and making a work to show people and someone else is coming in and trying to do the same after you've shown interest and commitment to doing it. There's more of an underlying "I think I can do this better than you" to it.
Also with stuff like MTL and such it's like going to a con, seeing someone cosplay the same character and they're only doing it because they're popular and they actually bought the cosplay off someone else.
In the end, people can enjoy seeing two of a cosplay but you'd be hard pressed to find people reading 2 translations a manga and going "wow, 2 cakes".