1st off, people grow, change, move away, move on etc. You may be using marijuana as a scape goat for simply the way life unfolds at times, but I cant tell you how to feel about that.
I do feel however that the 'gateway' argument is fatally flawed. Actually I think if marijuana was legal, it would be LESS of a gateway drug. Think of it this way: why do people not blame alcohol as being a gateway to harsher drugs? Its because alcohol is legal. The person that chooses to drink knows that as long as they aren't drunk in public, driving drunk, etc. that they are in no danger of legal consequences. If you smoke marijuana in a state/country where its illegal, you have now crossed a line into doing something illegal. Its now much easier to move on to something harder, since you're already on that side of the fence. Whereas the person drinking alcohol has not crossed that line. While the "addictive/unwell" person may have tried those harder drugs regardless of whether marijuana even existed. When alcohol wasn't enough they would still have tried the harder things even if marijuana didn't exist, would have just been one less stepping stone. In a world where marijuana didn't exist, would they say alcohol was a gateway drug? Idk, but would bet that they would. To take it even one step further, if alcohol and marijuana both did not exist, those hard drugs still would and even more people would be using them.