This was an effort to protect the economy from being ground to a halt by destructive litigious action and make courts more efficient. Not to increase liability and accountability within the corporation. Which is why nearly every western country has done the same... it wasn't a conspiracy to protect wealthy people from being punished.
Like many regulations that fail to affect idealistic change, it was done with good intentions and there hasn't been a strong enough support for an alternative to solve this issue... or, less likely, maybe no rational alternatives really do exist.
The simple fact is shit rolls down hill in all big organizations and I'm not convinced it won't happen if corporations weren't singular legal entities. Top tier executives have a way of protecting themselves, while the lower staff tend not to have such protections.
Removing this 'corporations = people' legal structure would incentivize internal deflection to lower levels as a legal strategy instead of the company uniformly fighting back against allegations - making it risky to be a low-level manager and highly disincentivizing employees from taking any real responsibility that would involve legal exposure (aka a huge percentage of management and entrepreneurial jobs).
Ultimately, the tough reality is that it might actually make sense to treat the company as a singular whole, as potentially there are hundreds of people involved in any major corporate incident. Which would be a nightmare in the bureaucratic mess that is the modern justice system.
That said, I'm not 100% convinced that courts can't use common sense to figure out direct liability and involvement within the company, at an individual level. But common sense has never been something the courts or government policy have been known for, at least in the last half-century. The modern justice system has entirely been modeled around the lowest common denominator. Which is very apparent if you've ever tried to challenge something as simple as a traffic ticket in court.
Given that legal/regulatory environment which it currently exists within I could see such a change being abused and being massively inefficient. Especially considering how difficult it is to prove a single persons involvement in a normal crime, let alone trying to sue a company then figuring out 100 individuals culpability...