One quick check: review a shot and zoom in on playback - if the photo is sharp but the view looks blurry through an optical viewfinder adjust the diopter. Also make sure you haven’t switched to back-button focus; if AF is set to AF-ON only, a half-press won’t focus and it feels broken. In dim or low-contrast scenes, enable the AF-assist lamp and avoid flat subjects, and make sure your finger isn’t blocking the assist lamp on a compact.
Blur is often from chroma subsampling or limited range rather than the panel, so try the other input type or lower the refresh and check the OSD for RGB and full range. If a one pixel RGB pattern or a zoomed checkerboard looks crisp the signal is right and if not fix that before blaming the screen.
