Still just as "unfair" with the current system...
Everybody gets a 5% raise (or whatever the percent is in a particular year), even the

ty couriers. The company is encouraging mediocrity by giving everybody the same raise.
I work for a petroleum refinery. I was union for over 10 yrs as an outside operator and now I am a board operator which is management.
Anyway, I remember one of the "benefits" of going non union as it was explained to me was being responsible for getting whatever raise I could earn based on my individual efforts.
But, that's all bs, in any larger company, the efforts of one person to the overall output of that company are going to be very minimal.
The units I oversee make gasoline, diesel fuel, Jet fuel, kerosene. But we don't make all of the gasoline the refinery produces, there is another unit that further processes the Diesel we initially process, and the Jet fuel and kerosene markets aren't as large as the markets for gasoline and Diesel, and the refinery makes a bunch of other products from Crude oil that earn various amounts of money.
In other words, there are so many other parts involved within the refinery, that one person's ability to dramatically impact that refinery's overall revenue even if they are great at their job is extremely limited, unless you mess up so badly that you cause a catastrophic failure or an environmental violation that costs the company many millions of dollars.
So, I have found that earning "better" raises becomes about performing for certain individuals and developing personal working relationships with those individuals who give out your raises.
As far as merit based raises, I see a huge problem with them, either the tasks to get certain raises are easy enough that almost every employee can earn the raise with some effort which the company wouldn't want, or the tasks are so extremely difficult that almost no one can ever get them which the employees won't want.
I am happy that our unionized outside operators are basically what keeps most of management's pay going up every year.
So everyone else basically gets yearly raises of 3-4% a year.
To me this is fair since actually calculating, whose individual efforts contributed to what percentage of company revenue I imagine would be tedious and meaningless effort by the company in my job category and for most job categories within the company.
There is only so much money to go around better to just spread the raises to your own employees relatively evenly.
I am referencing large companies and kind of job categories within a large company that has a lot of employees within that job category. Like being an operator in a refinery or a delivery driver at FedEx
Smaller companies with fewer employees and certain types of jobs where your work is kind of unique within the company can lead to much more control over compensation because you can show your impact to the company's revenues.