Does OnePlus 5 use the same screen as OnePlus 3/3T? In the recent presentation, OnePlus CEO stated that because OnePlus thinks 2K resolution is unnecessary for a 5.5" screen, OnePlus 5 will continue using 1080p AMOLED as OnePlus 3 and 3T do. I've heard major criticism on the screen of 3/3T, so I wonder if there's any improvement on the screen of OnePlus 5.
Sort of.

The OnePlus 3T and 5 share the same display model. Pocketnow even wrote an article about it.

However after further inspection, only some 3T phones have the display model of S6E3FA5 (This is the OnePlus 5's display.) Others are S6E3FA3.

Therefore, only some of OnePlus 3T's share the same display as the 5.

Can't tell for certain but from this forum post, the OnePlus 3 shares a similar story.