It's definitely not acceptable.It's a form of White Collar / 1st World Corruption.
Taking money from people with expectation of value, while not providing that value is Fraud.
Woaaah there buddy!
Did you read the all of the OP's post? He's never been fired and gets middling to good performance reviews. Continuing to pay his salary implies that the company it's getting a fair deal. This is obviously not fraud in any legal sense.
Characterizing this dynamic as "White Collar corruption" is a totally warped, an in my view, offensive. If there is any corruption in this scenario, it's on the side of the employer. If the OP's situation is widespread within the company, failing to recognize and remedy it could very well be a breach of fiduciary duty owed to the shareholders. Not a lawyer, but I'm pretty positive that ignorance or incompetence is not a legally valid excuse.
In my view, the real issue here is that salaried employees are almost never compensated in proportion to actual value that they generate. A flat rate arrangement, assuming no significant bonuses, results in a zero-sum game with diametrically opposed incentives for the two parties. The employer maximizes value by trying to as much work as possible from the employee. And the employee maximizes his hourly rate by working as little as possible, with the ultimate goal of infinte dollars per hour at 0 hours worked.
The incentives become perfectly aligned if the pay is based on some objective measure of generated value. Moreover, I would would argue that it would be fairly straightforward to come up with a logical metric for every single position within a company that generates revenue. These can be proxies instead trying to estimate revenue growth or cost reduction to every single employee. Moreover, the dollars tied to a given position's reward metric would be subject to market rates the same way that salaries are today.
TL;DR - Don't hate the player, hate the game.