GameMaker and RPG Maker and other such tools (even major engines like Unity and such) have differing degrees of limitations.
The more limited the tool, the more constrained the designer is.
These tools are very very good, but, I don't care at all if something takes hard work. Duke Nukem Forever took 10 years to make. That doesn't make it a good game!
Whether the game was hard to make doesn't particularly matter. Whether the game is actually good is what matters!
The more focused-in to a specific type of game a tool is, the more identical seeming will be the games that come out of that tool. If two dozen games feature almost identical gameplay and almost identical graphics, players aren't going to be as interested (unless they are part of the same series of games). They may each have really fantastic map design, and really top-notch plots, which is great! But those are only two pieces of a multi-piece puzzle.
If Microsoft took Halo, changed the color of Master Chief's outfit, and gave the game a different plot and different levels, but the gameplay is almost entirely identical, players would revolt against it.
Games are mixtures of: Gameplay, Atmosphere, Story, Background lore, Level design, Music, Sound effects, Voice-acting, Graphics, and several other components. Saying, "My game has a fantastic plot" (great!). "Oh yeah, but the graphics are almost identical to that used in 20 other games..." (huh?), "...and the gameplay is copy+pasted from those same games." (Uh, I think I'll pass)
That's not to say some of those games aren't great experiences. But by and large, most of them aren't. So I'm taking a greater risk, and am less inclined to even bother playing (because time is a non-renewable resource), let alone paying. But if one becomes a huge hit, and everyone (outside of the community from whence it came) recognizes it as a fantastic game, then yea, I'd certainly play it or pay for it! In those cases, it ceases to become common sense to avoid them, and instead becomes snobbery and elitism to not play them.
The reason why the opinions about the game has to come from outside the community to be heard is because the people within the community are used to the similar gameplay and similar styles and see only the distinctions, in the same way my brain automatically filters out the similarities of my siblings faces, and focuses on the distinctions. In the same way, everyone from certain ethnicities looks almost identical to me but anyone raised in that culture tunes out the overall same-ness and hones down to the individual uniquenesses to help identify each other. The more time I spend around those ethnicities, the more my brain teaches itself to filter out the generalities, and see the specificalities. I don't drink wine on any regular basis. Give me a five glasses of different red wines, and they'll all taste almost identical to me - I'd taste the overall flavors which are strongest (and shared between all five glasses). Give someone who has drunk hundreds of bottles of redwine in his lifetime, and he'll tell you of their fine details, and ignore their shared traits.
If every game used Unreal Engine without any additional custom programming work... it'd also be bad. Unreal Engine is loads more flexible, so it won't narrow things down near as much as RPG Maker, but it'd still force certain similarities on every game. Those similarities would be undesirable - not because they would be bad in themselves, but because the engine would prevent other games from just being different.
But again, that doesn't mean GameMaker or RPG Maker are bad. There can still be some great games that come out of them. Ninja Loves Pirate (GameMaker, circa 2006) is one that I've heard is really polished and worth a play.