Question Why does my moitor run some games poorly

Aug 14, 2019
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I have a samsung 27 inch curved monitor with a 72hz refresh rate. It runs some games flawlessly but other games are unplayable. Even something like minecraft. And i have an rtx 2070 an i5 9400f and 16gb ddr4 so i dont think it is my computer that is slowing me down. The rtx 2070 is an asus strix card and i have an x52 kraken 240mm aio for my i5 9400f so thermal throttling is a non issue, should i just get a new monitor?
 
Aug 14, 2019
6
1
15
full system
CPU: I5 9400f at 2.9Ghz boost to 4.2 or so
GPU: rtx 2070 8gb asus strix
PSU: 650 watt EVGA 80+ white
RAM: 16gb of white ballistix sport ddr4
Motherboard: Titanuim mortar MSI B360m
CPU COOLER: X52 kraken from NZXT
STORAGE: 250gb ssd, with 1tb harddrive
MONITOR:https://www.walmart.com/ip/Samsung-...AMD-FREESYNC-HD-LED-Monitor-C27F396/117633165, when freesync is turned on the refresh rate goes to 72

i mostly have problems with all games. On rise of the tomb raider cpu temp stayed below 40 degrees and my gpu stayed under 55 degrees. The cpu usage was in the 50 to 60% and gpu was around 25%