Without personhood, we'd have to know which persons within an opaque company structure were responsible for wrongs against us in order to sue them directly instead of just being able to sue or fine "Walmart" or whomever.
Before personhood, if a corporation had wronged you, you were limited to suing its trustees, its charter, or petitioning the government.
With personhood, I don't need to know who at McBigCorp decided to dump that sewage into my stream, I just need to know that it was done. I don't need to go after the trustees directly. Accountability is centralized, and the corporate entity likely has deeper pockets than the individual I might've sued for recompense.
So yes, corporations existed before corporate personhood, but they were more hazardous to public welfare and had limited remedy to abuse. The East India Companies and the railroad barons of the world were allowed to run roughshod until centralized accountability was imposed.
Aside from that though, we have lots of other enforcement mechanisms that we don't avail ourselves of for lots of reasons, some rational, some not. We can imprison executives, as we've done with Theranos' Elizabeth Holmes, Bernie Madoff, Jeffrey Skilling, Jordan Belfort, Martin Shkrelli, Donald Blankenship, etc.
We can also mandate compliance or impose oversight, mandate public apologies, ban companies from engaging in certain business activities (thinking HSBC being banned from financial services after money laundering,) impose corporate probation, mandate recalls, clawbacks, or probably lots of other things that don't immediately come to mind.
That we typically just impose financial penalties is probably a reflection of our values as a people or a judicial system or our government's willingness to collect fines, but we should not pretend that it's the only available option.