The rules don't control your players and don't run your game. You run your game and the players control themselves. The rules are there to help you have a good time when you need them. If you all agree on this:
"There’s no winning and losing in the Dungeons & Dragons game—at least, not the way those terms are usually understood. Together, the DM and the players create an exciting story of bold adventurers who confront deadly perils. Sometimes an adventurer might come to a grisly end, torn apart by ferocious monsters or done in by a nefarious villain. Even so, the other adventurers can search for powerful magic to revive their fallen comrade, or the player might choose to create a new character to carry on. The group might fail to complete an adventure successfully, but if everyone had a good time and created a memorable story, they all win."
Then it's exceedingly easy to see how the choices the the DM and players make during play either lead to "winning" or not. This includes the use of the feats under discussion. Players can make mistakes, of course, such as making a choice that isn't very fun for others or doesn't lead to a memorable story. But once they're aware of it (e.g. their feat choices and use thereof are trivializing difficulty or overshadowing their friends), there is really no excuse continuing to engage in that behavior in my view.
The rules serve as the contract that everyone agrees upon as to the type of game they're going to be playing.
I mean no offence by this but your style of DMing, whether it's what the basic rules say, is not my cup of tea.
I'm sure you're a fantastic DM but I like rules not rulings. I don't like rulings not rules. I take great comfort and satisfaction in reading the rule book and knowing that is the game I am playing, not the game you've created in your head.
I am not alone. There are lots of players like me - it's one of the reasons pathfinder is so popular.
We like to do things as RAW as possible and when there are issues with following RAW, that's when we house rule. We also like playing with feats, and banning all feats because there are a couple of problem ones is not the solution.
Self policing is an option, you have to know what you need to police first, and that only comes with experience. What about your first play through of D&D? You're going to run into issues with these feats on your first go, especially if you approach the game like pathfinder, 3e, and even later versions of 4e where you needed to min/max to be effective in combat.
And low and behold it has causes issues on first play-throughs at tables. I've seen one group have such a first bad impression of 5e they stopped playing it, and I know another poster who found the EK + SS combination ruined his fun as a DM so started a new campaign.
What do these feats really bring to the game? What does the game lose by removing them? I say there's far more to gain by removing them than by keeping them in there, and its certainly not a player issue. It's a design flaw.