A big thing to understand is that in stores, they are often using 4K content which has been optimized to deliver the absolute best it can possibly be with punchy colors and very high encoding rates for the absolute best possible image.
This many people are comparing to their Comcast cable TV signal at home.
Or worse... Streaming from Netflix.
Garbage in, garbage out, should be the first level mantra. Blu-ray Disc currently offers the absolute best quality image available to your display right now, and that comes from 30Mb/s encoded video. Any 4K streams are typically 7Mb/s, maybe a bit faster, but nowhere near what Blu-ray is giving us.
So, no source content is an issue. A big one. Once you leave that specially created demo, you are feeding your TV the same junk you are already looking at.
But, a better TV with solid contrast, good brightness, good black levels, great shadow detail, etc. may very well be an upgrade to whatever you happen to be currently looking at.
I have a upper mid-level Samsung plasma which replaced a Pioneer plasma. The Samsung looks very good, and I've seen nothing which looks clearly better than it.
Still, I would consider going from my 64" diagonal to a 80"+ sized diagonal that looked good.