JonnyDough has hit the nail on the head but I think it points to things we need to educate the new generation of PC gamers to. Many components of a good gaming PC are not a purchase but an investment. A good monitor should give great gaming for 4 to 5 years. Spending a bit more now means you do not spend later and gives a better gaming experience.
Grab your typical $170 monitor, 60Hz with a TN panel. You might get an IPS but it is not a great one. Not compare that to a high quality TN at 144Hz, or a high quality IPS with Freesync. How about higher resolution or the Ultra-wide experience. All of these impact the gaming experience and improve it.
Do not buy your monitor for just today but for tomorrow as well. You might not have the hardware to push it today but these monitors support lower resolutions. That 1440 ultrawide might be a bit much for your system now, no worries it does 2560x1080 perfectly. Invest when it comes to a monitor and realize your purchase should be great 5 years from now.
I personally want a curved 20-30" Ultrawide 1080 monitor with 60Hz Maximum refresh and G-sync/Freesync options as addon modules
Well bad news for you, anything under 34" on a monitor make the curve a gimmick and have little real positive impact on the experience. The smaller monitors are not wide enough for a subtle curve to have effect and the curves that do effect them are too deep.
The good news for you is that while Freesync will never likely be an "add-on module" is becoming more common and should eventually be a standard in monitors. The addition is not a big deal for the monitor makers, just a choice with little to no cost additions.
4K is pointless when you sit two feet away from a small screen.
Not many Graphics setups will see the benefits of fps more than a 60Hz refresh, if we can even perceive it.
I'd much rather buy a monitor which can play a game at 40-60fps with no tearing than a more expensive one at 40-144fps
I agree with your point on 4K, you need a really large monitor to use 4K effectively for productivity and for gaming it has less impact on the experience than going ultra-wide. I also agree that the majority of gamers play within a lower frame rate range than the enthusiast market contends. I would say 75 to 30 FPS is the range most gamers play in.