If you trade professionally, you will have to deal with tax implications, but that‘s your job, so it‘s fine.
If you are just a small investor staking some coins, this decreases the burden on you.
How does this benefit big players at the cost of retail investors?
Any regulation is an advantage to large over small, at the right level of large vs. small, since the burden of optimizing to win is more easily borne by the former. In some cases, it's just more obvious.
Previous situation: You had to hold your staking rewards for 10 years to be able to realize your gains tax-free. When simply buying and holding, the term was 1 year.
New situation: You have to hold your staking rewards for merely a year (like buy&hold) to realize tax-free gains.
Reducing the amount of time before being able to realize tax-free gains benefits both big and small players. (Right?)
However, I think the previous 10 year term was more burdensome on individuals than institutions. Maybe that is where we disagree?