Apple's latest iPad Pro tablets use a mini-LED backlit LCD (which Apple refers to as Liquid Retina XDR). This relatively new display technology is seen as a way to achieve almost OLED-quality contrast ratio and an improved power consumption as the thousands of small LEDs enable very small dimming zones.
While most reviews of the new display are quite positive, some users are complaining of "blooming" - the edges of bright objects on dark backgrounds tend to 'bleed' as the dimming zone is not small enough.
I am not sure how serious this problem truly is, but it is highly likely that OLEDs perform much better in this area. It is likely indeed that miniLED technology, while able to improve upon regular LCD quality, will not be able to compete with OLEDs or other emissive technologies in the longer run.
Blooming is inevitable with backlight zone larger than one pixel.
The current MiniLED backlight is like JPEG: large single-color areas are uniform, but object edges are dirty.
Once each pixel gets its own backlight, we get perfect contrast while still having other LCD drawbacks, including slow response and not quite clean colors.