If a city enforces a new speed limit somewhere and only people living outside of the city break that speed limit, you argue that the law isn't applied equally because no resident of the city has been fined so far?

That's the most backward way of trying to prove a point (without even addressing whether DMA and GDPR are a good thing or not, just based on that...)

None of the gatekeepers are EU companies.

You might say that's proof of it being unfair, but can you name a EU company which should be one? I can't really think of one, US companies are just so much bigger on the internet, even in the EU.

Looking at the other law you mentioned, GDPR, there are many EU companies receiving GDPR fines.