That's not what I meant by using 7 as an average. That's just only playing through and rating games that you finish a 7+ because you're dropping anything that isn't what you consider "above average" and worth finishing, That's you having an average vote of 7 not you voting 7 as average. You would still be voting a 7 because you feel the game is above average instead of "boringly average" as you put it. What I'm talking about is playing through an entire game, feeling that that game is of average over all quality as a whole and still rating it a 7 because you've arbitrarily decided 7=average instead 5. Doing so completely defeats the point of a 1-10 rating system. If you found something average it should be rated around a 5 because that is how a 1-10 system works. When people start using it differently than 1= bad 5= average and 10 = masterpiece and start making up their own rules as to what score signifies what the whole thing becomes completely pointless. Go look at, say, MAL's rating system. A lot of people there think a rating of 7-8 means it's an 'average" quality show and anything under a 7 means it's horrible crap. That's not how a 1-10 scale works and because you have some people using it properly and some not the whole thing is skewed and inconstant. That also isn't even including those people who do things like spam/troll vote things up/down just because they are popular or vote anything and everything they enjoyed a 10 and everything else a 1 which again isn't how a 1-10 system is supposed to work.
Most/a lot of people do complete games that are only "average" because by it's very definition the majority of them are average as that's what the term means. Like I said the scoring systems are almost all pointless since they are constantly used improperly and even if they weren't there is still the fact they are mostly unreliable because there is no context to it. At least with written reviews even if they are short, biased and stupid there is context there for you to notice that and then decide which to pay attention to and which to ignore. There is none with the number rating system on most sites
Honestly tho I don't see why a score would have an effect on someone's enjoyment. Even if all the systems were being used correctly and consistently they are still just a collection of other random people's opinions. No matter how much other people loved/hated something it really shouldn't change how you felt about it. Tho I do understand why someone might get mad or upset when something they love is rated poorly or the opposite but that's an entirely separate matter. If you loved say. FS/N and a bunch of people told you it was shit (rated it low) it might bother you but it shouldn't actually make you enjoy it less.