Yes, typically safe. If it overheats it will likely thermal throttle and lag on intense graphics tasks.

When I was in college, I had a extremely weak netbook that I would carry with me and even that Celleron processor, without a graphics card, could run the original Torchlight game with minimal lag. I play Minecraft on a Dell XPS 9370 with an i7 and no discrete graphics card all the time, I just can use shaders or excess mods. It doesn’t feel snappy like my desktop, but it is 100% playable, even at full resolution.

Some games won’t run well on weak hardware, but if you look for the recommended specs you’ll see which developers went put of their way to support weaker hardware.