Thank you for giving it a shot and sorry you didn't have a great time! The description does mention being able to slow walk with Shift, which as a matter of fact is something I added because of Rust, although sadly I didn't have time to explain it in game.
And the second weapon is, in fact, an extremely gameplay changing feature that lets you move through the map - albeit it is optional, much like the majority of the content in the game. So I guess it only counts as a Metroidvania if you go out of your way to look for the Metroidvania!
Part of my design philosophy was that an incomplete experience is still a valid playthrough (hence why "there's no shame in giving up"). I didn't want there to be any "fodder" bosses because in the end, the true final boss is the one that makes you give up. After all, statistically speaking, the majority of players don't finish their games, so you could say giving up is the most genuine experience!