Your argument essentially boils down to "it's legal so it's okay" which ignores that all manner of horribly unethical things remain legal because it suits corporations. 

Using gaming to push gambling on little kids is still legal in much of the world but is a horrid practise, as is all manner of deliberating screwing the consumer to squeeze out more profit for shareholders.

Are there any M-rated games at all that you enjoy or are looking forward to? Would you be okay with them being completely banned because some bureaucrat or activist decides they're immoral?

Something can indeed be both legal and unethical, but that's not the case here. I don't really care what marketplaces decide to sell, they're running their businesses in whatever way they think best suits their strategies

There are bookstores dedicated to selling Christian books, and those stores may avoid LGBT content. There are restaurants focused on vegan food, and they don't serve animal-based products. There are TV channels and streaming services aimed at families, kids, and teenagers, and they avoid R-rated content

As long as no one is banning the game from being produced or sold, there's no real problem to fix here

Banning them from being sold entirely is the next step in this process and what we are headed for, it is the endgame of the people who behind this push.

Then be mindful of the problem when it comes. And be proactively engaged in politicts, this is what you can do 

The problem has already come, it's happening right now. You are right in that proactive engagement is key, and part of that is raising objections and awareness.

Posting on VGChartz may not change the world (which is why I'm active elsewhere) but we can still discuss it.

They banned Super Mario Bros. 2?

If Google doesn’t desire to platform a product, they should have every right to exclude from their shop. It’s not like Google is working with other storefronts to make the game impossible to legally purchase.

Imagine if somebody start setting up political signs on your property or plastered posters in your privately owned store (in the hypothetical scenario where you own a store). Should you not be allowed to take down these posters? It should be within the business owners’ rights to do so IMO, no matter how big nor small.

Google had no problem hosting it before; the only thing that changed was that authoritarians pressured them to do so.

The people who are pushing this agenda of banning and censoring anything they deem immoral are lobbying every storefront to follow Google's lead, their goal is for it to be banned from sale everywhere, from Steam to Switch to Playstation. Google simply caved first.

They're also lobbying governments and politicians to ban them entirely under the guise of "think of the children". In my country many websites are already being blocked as part of this push. 

The whole freedom of expression thing just doesn't hold up when we're talking about an individual company like Google. Forcing Google to sell a game they've decided they don't want to sell would be a denial of their freedom of expression and an interference in their business decisions. They should be free to make whatever decisions they deem to be in their best interest, just like any other person or legal entity.

The real problem here is how much power individual companies have in the Tech space. Companies like Google, Apple etc. Just represent too much market power and their choices have consequences that feel far beyond what one single company should be able to achieve.

Out of curiosity, you seem to suggest that if every company banned this game that wouldn't be an issue because the government didn't force it to happen. Is that you position?