You should NOT be able to tell your TV is dimming whatsoever. That just indicates something may be wrong with the power supply of the TV itself, or that your eyes are getting older... yes, that happens.
Many of us, I expect, have televisions well over ten years old that still look fantastic. But, the main thing with televisions is starting with a decent display technology from the start, then maximizing what it offers and understanding that all televisions seem to have some sort of tradeoff. OLED is dimmer than LCD, but it has, by far, the best overall contrast and image quality with Sony typically winning for best overall quality with their A95K. But, the LG C2/G2 panels really are solid performers as are Samsung OLEDs.
When it comes to LCD and bright room viewing, typically it is Samsung which wins for best overall with the QN95C.
I wouldn't touch LG for anything but OLED, and I wouldn't likely step away from Samsung, Sony, or LG for a higher end television purchase at this time.
Room conditions and screen size also come into play in getting the best overall television experience. Quite often, people go with sizes that are far smaller than what they really should be using from a typical viewing distance. I would say anyone 10 feet or more from their screen should be in a 80" or larger television class, which can sometimes strain budget. Especially with OLED displays.