If it only happens in the evening, it could be due to your ISP doing something called throttling. This is where they significantly throttle your connection during peak hours, often causing significant issues for gamers. This happened to me once after switching ISP due to them lying to us, so I immediately used a cancellation clause in the contract and ditched the ISP.

Otherwise, increased ping and packet loss is something that has been happening with an ISP called ntt on the way to the FFXIV servers or due to DDoS attacks. Usually you can get around this by using a VPN. Forget all the reasons youtubers give for using a VPN. This is an actually good reason to use one.