You don't finish them, because you go in with the intention of breaking them, because that's where your main source of entertainment lies. Finishing the game without being bored after having broken the game only comes secondary to you.
Not really. My main source of entertainment from games is as follows:
1. Good story.
2. Good characters.
3. Challenging, but fair, gameplay.
4. Breaking the game.
I start most games with the intent of playing them "as normal". The problem lies largely in the first three issues being... non-existent. Or, they dangle something I see as "necessary to get as quickly as possible" in front of me, and so I go break the game to get it.
Breaking a game is something I enjoy doing, but it isn't my primary motivation to play them. It's just... well... notoriously easy to do to most games because most devs... well... kind of do things very badly.
So, if your game has a boring story, uninteresting characters, your gameplay is boring, repetitive, or uninteresting... I go break your game as the source of fun I'll have with it.
Then, once your game is broken... There's nothing left in your game to have fun with.
"Breaking" a game doesn't even necessarily mean to exploit it. You can over-level by grinding a lot in RPG's, and in turn "break" the game by cheesing every challenge with stats alone. Considering grinding for levels is a way for developers to allow bad players to finish challenging content; doing so as a player who's good enough at the game to not require the extra levels from grinding, obviously results in a boring game. Because fun in gameplay, to most people, comes from overcoming challenges, not from facerolling everything in sight (which is fun, but only in small doses).
If a game can be broken because it's bugged or badly balanced, then that's on the designer. If it can be "broken" through intended gameplay design, then it's on the player. "Breaking" a game because it has the intended option for you to grind up levels to ease the challenge, and then complain the game is boring and too easy because you spent 10 hours grinding trash mobs before going in, then that's on you, not the game.
I would make the opposite argument. It's very "basic" and "uninspired" and non-creative to have a combat system that relies entirely on stats. Such systems are inherently designed for grind. If your combat system is based entirely on stats... you just have a terrible combat system.
Engaging combat systems rely more heavily on player skill than stats of their characters and equipment. Boring combat systems rely heavily on stats and stat sticks.
It is inherently bad design if your game can be steamrolled by just having more stats. Likewise, the argument of "it exists so players who aren't good enough at the game can still just brute force it" indicates very bad design. If your player can and DOES brute force the "challenge" of your game, you screwed up somewhere. You didn't sign post properly, you forced an over-reliance on stats, you allowed there to be an over-reliance of stats, you made your combat not that engaging so players weren't doing it that much because it wasn't fun, etcetera, etcetera, etcetera.
Now, don't get me wrong, there are games that revolve around stats and there are games that make that fun. However, the primary fun of those games isn't usually in "overcoming challenges". It is usually in a massive skill tree, lots of different builds for characters, customization, getting small increments of power at regular intervals, and other things. The primary gameplay loop of games that revolve around stats and remain fun, isn't anything to do with combat in most cases.
However, if you're making an RPG and your combat is so boring that players aren't engaging in it much, are actively breaking it in order to render it easier, or are overleveling as a means of bypassing it... That says your combat is badly designed and you didn't design it for "fun" only for "functionality". At which point, you've become an EA Executive.