Well, even though there are "Morty is disabled" comments from time to time inuniverse, Morty has shown he can be pretty smart when he is focused/needs to do so. During the pilot, he is quickthinking and uses the Gravity Shoes during the chase sequence, for instance, and even Rick gives him props.
And let's not forget Rick mentioning that Morty should focus on science and, during his sacrifice, be better than Rick. I certainly cant see Morty being "disabled or somewhat incopetent". It is true, however, that he is gullible and does shit decisions.
Also, Rick getting drunk, setting up bombs and all isnt something common really. Morty has been around Rick for long, he knows Rick better than anyone else, which may be a reason why Morty is constantly being shown as smarter in Season 4 (learned how to use the tech that messed up bodies in the latest episode, the bomb feat, etc.) and more capable. If anyone were to go around, hearing and learning from the Universe's Smartest Man (I do believe Rick has that title, doesnt he?), they'd get quite smart. And with Morty being Rick's own blood and Rick seeing potential in him, I dont think he truly is a dumbass.