Overwatch is very CPU intensive, so I would say you will need to upgrade to a newer CPU with more cores etc...
Also, your Ram is quite slow for a PC now..
Check what you have running in the background too, if you have a lot of stuff using your CPU it will affect the Frame Rate..
Obviously with the price of PC parts at the moment, it will be expensive to upgrade everything.. But that is what I would do ie: new mobo, cpu and faster RAM..
AMD Ryzen 7 3700x, Asus Tuf Gaming RX 6700 XT, Asus TUF Gaming x570 Plus, 32gb G.Skill TZ neo 3600mhz, Samsung 980pro 1tb NVME, Samsung 970 EVO Plus 1tb NVME, Lian Li Galahad AIO 240mm, Antec Titanium 1kw.