If society doesn't value what IBM produces then they'll go out of business. There are many factors to optimal organization size, and there are different ways of handling acquisitions that can preserve the acquired organization to varying extents. I work for an org that got acquired by IBM and my job (and org) has been remarkably unaffected. Just different folks enjoying the profits.

Like all things, there is much more nuance than "big corporation bad."

What's the value to society of large companies not getting larger? What is even the relevance? Does everything have to be judged in terms of its value to society, and if so, why? Should we talk about your value to society?

You're arguing for a draconian regulatory response (it sounds like) to what should be a market issue.