Alien Zombie Megadeath doesn't feel old, it actually strikes me as fairly modern and a product of its time. The only thing it about it that is old is the way it makes me feel. Just the name of the game makes me feel old. It is so desperately trying to be cool by throwing tired tropes in a way that it perhaps hopes is ironic. The claim of being “old school” is just another sort of pretension. It wants to re-create the simple colourful joys of past, when a plot was a one paragraph intro before the shooting started but while it throws the story out the window what is left doesn't measure up to the old classics it is trying to ape.
I'm struggling to place AZM in a genre. It feels half way between a platformer and a twin stick shooter. It plays most like a twin stick but your little spaceman is affected by gravity (which is odd if you think too much about it) and so can only run along the platforms but each level is made up a half dozen or so liner platforms, all of the same length, stacked above each other so it is like jumping about on some sort of shelving unit. You can also only shoot left and right which makes dealing with the enemies that attack from above and below a pain in the neck and ♥♥♥♥ respectively and deaths to them just feel rather cheap. It is a twin stick that robs you of the freedom of movement and attack, the joy of which is the joy of twin stick shooter. It all just feels, well very busy but not very exciting. Very rich and colourful and full of features but not much fun. It just doesn't feel quite right to me and so I struggled to have fun with it and I don't feel I can recommend it. On the other hand if you enjoy the feel of it then there is certainly a lot of it in terms of content. Utlimately though, If this is old school then I think I am ready to embrace progress.