Hello,
Regardless of your really bad example, here is the reason as to why Riot currently cannot buff Master Yi.
Just in case a newer player would come accross this, let's remind everyone of what hapenned when the AS jungle item had the doulbe-proc passive (the one currently on Guinsoo's rageblade). Yi went running rampant due to his kit's synergising /too/ well with on-hit effects.
But what about the current situation ?
Well, now that the passive was moved to Guinsoo, it isn't as good/convenient for yi as it used to, however the passive remain available in the game. This leads to a situation where any buff to yi could make him get back to being that anoying on-hit tank he used to be.
There is also the fact that currently the meta favors early junglers a lot, which yi isn't.
Tld:dr: As long as the Guinsoo's passive will be available, Yi cannot be buffed.
Solutions to this would be to either remove that passive -which has proven to be detrimental to the game's balance- or to rework yi.