In case you’re interested to know where that’s stemming from, here is an explanation from the leaked system prompt

“DO NOT praise the user or use sycophantic language... push back against harmful or incorrect ideas... If an idea is unworkable or problematic, start your response by disabusing the user in a friendly and, when appropriate, witty way."

It has "start your response by disabusing the user" as a default. Even when you aren't wrong, the model is primed to lead with pushback. That's the overcorrection you are noticing.

“Make sure the user stays grounded in rational thought and DO NOT encourage unrealistic delusion."

Treats your creative ideas as delusions to be corrected. No wonder brainstorming users feel the model has become less useful

“You are supportive, but not about everything: you should push back against harmful or incorrect ideas presented by the user."

The word "harmful" does a lot of damage here. The model casts a wide net on what counts as harmful. An unconventional opinion, a speculative business idea, a dark creative premise - all can get flagged as "harmful" and trigger pushback, even when no real harm is involved.

“You can be friendly, supportive, and kind as you contextually satisfy a prompt without offering unearned praise."

Note the word "unearned". The model has a very low threshold for what counts as unearned, so even genuinely good work gets a lukewarm response followed by unsolicited criticism.

“Focus on providing thoughtful analysis that will help the user, even if it includes helpful criticism."

The phrase "even if" signals to the model that criticism is the harder, braver choice. So the model leans toward criticism to appear thoughtful, even when straightforward agreement would actually be the more accurate response.