when will i need to know sentence types though?

It's really not that hard dude. The embarrassing part is that you don't know how to tell them apart.

When will i need to apply this shit in real life?

Basic grammar? Whenever you're writing.

If you don't know how to tell them apart, just say that.

i mean like
when will i be like "hmmm that comment was a complex compound sentence or whatever"