The idea here is that it's not your personal choices which are causing climate change or fishless oceans, it's "big industry" and we need regulation to fix it. Focusing on personal choices is a distraction from the systems we need to put in place.
History and scientific studies have shown that personal responsibility is the most effective way to create policy change and install the systems that will help. So by doing this concern-trolling game where you don't want to take any personal responsibility, you are actually actively hurting the environmentalist movement you are pretending to care about. This vlog brothers video is a great summary of the topic of how personal change impacts policy. So this game carnists play hurts the causes that carnists claim to care about.
How humans behave aside, this is just another case of people pretending to not understand how supply and demand works. Industries don't make stuff if nobody buys it. By buying it, you're creating demand for the product and normalizing it, and contributing to the damage. Carnist-environmentalists recognize this when people claim to want to boycott companies, vote, or make any other easy personal change that has a potentially widespread impact, but somehow that all gets set aside when it comes to veganism. Curious how that happens.
So let me get this straight: You don't want to eat vegan food, you want to keep eating your surf 'n turf. So what's the big brain idea here to reduce emissions from the single largest source of climate change, or to stop overfishing? Regulations won't make beef or fish less environmentally destructive without limiting consumption, or at least have historically failed to do so. This leaves only one option: regulations would need to legally force people to eat less meat. But, then carnists would go down kicking and screaming. So ultimately, there are really two options: 1. take personal responsibility now and thereby encourage the creation of policy, or 2. Do nothing, complain that "systems aren't in place", and then hope that laws are magically put in place that force you to action that you didn't want to take in the first place.
It seems pretty clear that this is just pushing responsibility off and pretending to care, hoping someone else comes along and fixes a problem that you're too weak-willed to do anything about. Slacktivism at its finest.
You're still killing an animal that doesn't want to die for your own entertainment. It doesn't matter if you can shove off the environmental and human impact onto someone else.