the place that employed them ceases to exist?

And give up all the profits that are to be made? To clarify, this advocacy isn't against small, local, Mom'n'Pop type stores, but against large, corporate chains. They have enough economic weight to not simply collapse from it.
They'd factor the losses (shrinkage) and Loss Prevention cost into the price and raise it accordingly. That would socialise the losses, meaning the rest of the customers would pay extra to compensate those that don't (while the company execs and shareholders maintain their profits).

If that drives more people into stealing, they'd need to find some other way to profit, maybe lowering the prices to encourage people to pay instead - better a smaller profit margin than none at all.

If it actually got so unprofitable that it would have to close, we'd have a case of Tragedy of the Commons where individually beneficial behaviour at a larger scale ends up hurting everyone, including those who initially benefited. This wouldn't just affect the workers but also the customers.

Most likely, any community approaching that critical tipping point would recognise it (whether on their own or by official communications of those suppliers) and make an effort to counter-steer, whether by increased law enforcement, by social programs to help people afford stuff and keep the suppliers paid or by supporting local stores that end up cheaper than the big ones. Faced with the threat of paying or not getting anything at all anymore, people that can pay probably would, if only out of self-preservation.

But let's assume that the Tragedy did play out. Let's assume a smaller community for unspecified reasons ends up so impoverished that they collectively simply cannot pay for necessary things even at break-even prices. No external stimulation projects are made to relieve them. Large stores close because efforts to compensate losses have failed. Supply of necessities dries up.

Those that have wealth from outside the community's own economy may be able to afford going elsewhere for their things. The rest (both the initially unemployed and local businesses depending on their custom) would either migrate to some place they can find work or starve. The wider economy that depended on economic activity or labour from that community would suffer too.

That would be a catastrophe, both socially and economically. It wouldn't be the fault of shoplifters alone, but also of the entire machine and every exec that let it get to the point where all the labour and profit to be gained from that community dies out. If you have some production in that area, the cost of living rises because the stores raise prices, and you refuse to pay your employees more to the point they can't afford to stay there working for you, you're just as fucked as the people.

What could be done to prevent that? The community as a whole could form a bargaining entity, forcing those that want to profit from them to the negotiating table for acceptable terms. It could attempt to establish its own local supply. It could also resort to violent action against other communities that left it to its fate.

A smaller could melt away into other communities around, like you sometimes see with rural communities where younger people opt to move closer to cities if employment prospects at home are miserable. A larger community might see economic fugitives seeking better opportunities elsewhere.

Most likely, they'd be forced into some agreement, even if it might be an exploitative one, whether by necessity or by force. The balance here would be dictated by the relative size and power of the parties involved. If the community in question can exert enough economic power.

All in all, it's unlikely to ever get to that scale, because too many people have stakes in preventing that. If it did, it wouldn't be the fault of shoplifters alone, but of collective social and economical mismanagement.

Rationalizing theft because you want to feel like you're Robin Hood is just that, a rationalization. It's not the reality.

I'm not trying to feel like Robin Hood. That would require me to engage in coordinated heists with the intent to distribute the stolen goods at the expense of the parasites that sought to squeeze our misery for their profit.

My intent is, quite honestly, to foster awareness of and disdain for the greed of profiteers. They're in the minority, they need us to do the actual work and buy stuff from them, and the only reason they can exploit us is because we tacitly let them. That is the reality.

Collective disobedience could force both the employers and the stores to the negotiating table. The critical factor here would be the size of the disobedient group: the more people are on board with forcing change, the more change can be forced. Hence, if I want things to improve, it's in my rational interest to convince people to join my efforts (and really, the efforts of various other flavours of leftist all align in that respect).

There is no emotional desire to self-aggrandise here, no "want to feel like". There is simply an acknowledgement of reality and a wish to change it for what I consider to be the better.