I'm not shaming. I'm pointing out that they are not blindingly obvious and unavoidable. One has to search for them. Intentionally searching for something, finding it, then complaining that it's there is really weird to me. Not that you are complaining, but others are.
But that is simply incorrect. You don't have to intentionally search for the trade bug, just trying to get a better deal with the AI will trigger it. You also don't have to search for the production overflow bugs, just chopping a tree while building a military unit with a bonus does it. These are not some obscure things you have to jump through hoops to find, they are there in virtually every game. Whether you pay attention to what happens in the game in such detail that you notice these bugs is, of course, a different pair of shoes and a matter of taste. But for those who do, these are obvious enough that you notice in your first or at least your second playthrough that something is off, that you can't avoid it, and, if you care about such things, that may even render the game soft-unplayable (as in not worth your time for the moment). Perhaps they are not obvious to all players, perhaps only to a fairly small minority. But that doesn't invalidate the concern.
You also may not have properly considered how one should deal with the issue in MP games. MP games are all about eking out any advantage you can get over your enemies. Surely you can't realistically expect everyone to adhere to some house rules all the time, unless you only play with friends? While that is not a big concern for me personally, because if I do MP I only do it with real-life friends, but I can definitely empathize with the pain this would cause you if you are primarily a MP fan. Of course one may argue that Civ is primarily a single-player game, but if the devs feel that they have to add a MP mode, they should damn well make sure that it works and doesn't have too many exploits.
I understand that games are usually released unfinished (a lamentable practice, but that is what players like me, who still buy the game on release even though they know it's probably full of bugs because they don't care enough about their money, incentivize managers to do), and I personally view threads like this as reminders to the devs about which problems are in the game so that they feel more incentivized to fix them. So even if you had to intentionally search for exploits, if you never complain about problems you find, chances are that they won't be considered important enough to fix.