That's largely relative to your cooling solution. Mid 70s with an entry level cooler is just fine.Anything under @ 70ish °C is perfectly normal behavior. Even occasional jumps above is ok. Sustained above @ 70ish is when you need to re-evaluate what's going on.
While gaming my i5 8600k goes up to 68c is that normal and if so what shouldn't it go past?
What kind of thermal paste do you use? If it's some cheap stuff then you should replace it with something higher quality while running something like that. Also I'd say it's running fine just worry when it get's over 80 to 90 or more.