"This ad is dumb, but it's very funny."

Translation: Cette publicité est bête mais elle est très drôle.

[david527812]

Why not c'est instead of elle est

[RoslynJS]

https://www.lawlessfrench.com/grammar/cest-vs-il-est This link explains.

1. C’est and il est with inanimate nouns:

Like for people, c’est is followed by a noun that may or may not be modified by an adjective.

Il est can again only be used with an ADJECTIVE that describes the specific noun.

C’est une jolie maison.
Elle est jolie.

It’s a pretty house.
It’s pretty.

Ce sont des vêtements chers.
Ils sont chers.

They are expensive clothes.
They are expensive.

[jsrambal]

Can I use "amusante" instead of "drôle"?