Why do people get annoyed with thats what she said joke?

Never experienced anyone getting annoyed at that

That's what I said.

Don't know. I don't know what the joke is.

Example

I can't get this dirty mark off my car!

Answer, well rub it harder


Reply , That's what she said

Or this tree is over 100years old. Its a damn big one.

Thats what she said

Ah, thanks for giving it a bit more context.
Our equivalent in Dutch is "That's what the missus said last night as well."
It's only used in a setting with familiar people in a lighthearted, relaxed atmosphere.

I can get people getting annoyed with it. It's not something to often use as it'll wear very thing, nor in the wrong setting.
Timing is everything for such things :p

Sure timing is everything but we people are complex. So you never know when they understand humor WELL! Better to try it in a relaxed mode

It's not just a matter of choosing a relaxed situation. Humor is one of the trickiest things humans do.

Context and culture matters too, as well as reputation.

The exact same one-liner, such as "that's what she said" can result in big laughs for one person, and complete disdain for another, in exactly the same situation.

Main caution: be careful about what YOU are thinking as you say something. If "That's what SHE said" is clearly targeted at making the speaker sound smug and superior, it's likely to be poorly received.

It's more likely to go over well, if no one in the joke is being insulted.

So subtle you

There is this song called Whatcha say. For the longest time I was mishearing the words as “what did she say? All that she’d want to say.” I thought this song was about being ghosted and making peace.

I have to say I don't find it funny. But men seem to stay amused by it.

If every sentence is ended by "that's what she said" then it becomes annoying.

I bet you say that to all the boys ,

There's another

If “she” refers to someone:
That you know personally - mean
That you do not know - funny
No person at all really - just word play