Haha I definitely get the bit about the stigma against RPG Maker, don't necessarily agree with it myself but I have to admit it is pretty easy to spot most RPG Maker games which is why I was so impressed it took me as long as it did with yours. I think the work towards that will really help get some people that might otherwise be biased by it.
For the intro, I think you probably have it at a decent length. The initial conversation felt maybe a tad bit long but not that bad. I think that just comes from the fact the characters tend to speak like kids would which can be a bit roundabout at times. Otherwise I think the length is probably exactly where you want it. If anything, I almost felt like it jumped to the silver daze/weird world abruptly but that is likely more a me-thing so the current length is good. It felt like you explained all the necessary mechanics while still feeling pretty concise.