Can't see the Wood/Forest for the Trees:

If you can't see the wood/forest for the trees, you can't see the whole situation clearly because you're looking too closely at small details, or because you're too closely involved.

I don't think we can see the wood for the trees at this stage, so let's get an outsider to take a look at the project and give us a progress report.

Marcus is so focused on product details that he can't see the wood for the trees when it comes to the overall needs of the company.

Note: can't see the wood for the trees is British English, while can't see the forest for the trees is American English. Here the word for means "because of".

Persian: شتر را گم کردن و پی افسارش گشتن، اصل را رها کردن و فرع را چسبیدن