my pair of North Face rain pants are a lot lighter than older rain pants I used to own. They are also reasonably flat folded up , so I'm very much in the camp of it being worth it to have full rain pants.
The thing is, some rain pants are a lot heavier, stiff, thick, whatever, so you really do need to see them in person and feel and weigh them to know--pretty much impossible just looking at online store photos.
I'll look and see how much mine weigh.

and I used rain booties also, so with full rain gear, I don't end up with wet stuff that takes forever to dry out, and no matter what people say about sweating etc, your clothes and shoes are going to be a hell of a lot more wet and soaked without full rain gear.
And if too hot, you just take it off and you dry quickly.
When cool though, even if damp with rain gear, you wont get chilled, which can happen pretty easily, even in some summer conditions when the temps really drop with big thunderstorms.

I also have no problem putting on and taking off rain gear often when needed.

**my rain pants are North Face using the lighter membrane stuff that is less heavy than some goretex or whatever--they weigh 222 grams, or about half a pound.
I've always found that this waterproof layer technology works pretty good, breathes fairly well, and as well as being sort of light for what they are, they dry out in the sun or dry air fairly quickly.
I guess superlight sylon stuff will work too, a lot smaller and lighter.

I'll also go with others have said, about never regretting having good rain gear if rain and temps aren't great, no fun being overly uncomfortable vs a small weight penalty, unless you are racing or something.

I got a new rain jacket last year, a lot lighter and less bulky than my old one, same level of 2 layer waterproof layers as pants. Works pretty good all in all.