Game feel is important, arguably the important aspect of when it comes to engaging your players. Even on a jam about intentionally bad games :)
The two best videos I always send people who want to quickly shrink Unity builds are this and this. They are short and very generalized but they are a good way to start.
Other than that make sure your textures are a power of 2 and use Unity’s built-in model compression. Also make sure you’re using the most recent build method. Unity still has legacy support for older algorithms that have poor compression in today’s standards.