The designers can't control your players.
Yes they do. The rules are a control system. Sage Rulings help explain the rules that provide the controls to play the game. You can modify them to suit individual desires, but the rules set the parameters for play. The rules, numbers, and the dice system are the designers exerting control over you and your players providing you with a consistent, playable rule set.
What we can do as DMs is seek consensus on the goals of play the designers set forth (Basic Rules, page 2) and how to achieve them as a group. Achieving the goals of play is how one "wins" at D&D.
There is no "winning" in D&D, at least not in the traditional sense. I don't play for such an outcome. At this point, I don't need a Basic Rules Page 2. There has been something similar to Page 2 in every edition of D&D. Page 2 does not mean the game designers haven't made mistakes in the rule set.
If you're making optimal choices that fail to help the group achieve the goals of play because your CoDzilla character is frustrating everyone else, then you just caused the group to "lose" at D&D. Your choices, not the feat, is to blame.
You truly fail to acknowledge that rules can enter the game that can cause this failure without intention. This is a failure on your part to acknowledge something that has been true across every edition of D&D. You are in essence creating a false god in the game designers. That they can do no wrong and only the players can be blamed if the rules fail to provide an experience that doesn't abides by page 2 of the Basic Rules (Or whatever page of whatever edition that describes similar intent).
You seem unwilling to acknowledge that a player might choose a rule provided by the game designer that causes a breach of their own listed guidelines without intending to make the game no fun for others.
The designers make mistakes. They have done it quite often. They will do it again. If they correct them in a timely fashion, it helps all in the community reach the Page 2 guidelines of cooperative fun.
To be clear, I'm not trying to "sell" you on anything. I have no stake in your game. But I am bringing up things that I think are worth addressing and are often overlooked when it comes to these sorts of issues at the table.
You are definitely trying to sell your viewpoint. You believe the game designers have not made a mistake in the case of these two feats. That the players are at fault for not being self-policing. You haven't experienced any of the issues I have outlined or you just don't care about them or your players agreed to self-police leading back to no experience. Either way, this discussion has reached an impasse. Page 2 does not help me fix the game.
I have been doing this a long time. I don't need a Page 2 any more. I need a rule system that keeps certain options from overshadowing other options so I don't end up surprised at the table and have to take action to correct a problem. The player that used this feat did not know it would turn out as it did. As he leveled, the option kept getting better. Lo and behold, Houston we have a problem. My reaction was, "Damn. Wish the 5E designers had caught this little issue. I'm going to need to do something about it. I don't want another hard DMing experience in 5E."
I have no idea what your level of experience is with game systems. Mine is extremely high. I know when something is a problem. I usually know at what levels (or point level) and why. I make moves to correct it.
I do understand others will not see a similar problem for a variety of reasons. Maybe they don't play to high enough level. Maybe they like powerful martial damage dealers. Maybe they don't optimize. So be it. I know that using the RAW in the core PHB my players found a way to do an enormous amount of damage very quickly using GWM and Sharpshooter that otherwise would not exist without those feats in play. I will make sure to tone down their use to make encounters play out closer to the way I would prefer it in the fiction.