Looks like you've got a runaway worldgen cascade, where creating one new chunk forces another to be created, which in turn forces another, and so on until you run out of memory. A lot of pre-1.13 structure-adding mods (including Ruins) cause a bit of worldgen cascade. A little isn't so bad...but if there's a whole pile of it, you get lag spikes and even crashes. That's where you are,
Your log shows evidence of a classic worldgen cascade: a long chain of new chunk generation. While it is possible for Ruins to trigger a runaway situation, you almost need to maliciously configure it to do so. I'm pretty sure Ruins isn't the culprit here: of the 39 links in your cascade, only 4 of them are from Ruins. As for the others, 5 are from Gany's Nether and a whopping 30 are from Arcana RPG. I'm not familiar enough with those mods to say exactly what's going on, but I suspect your problem really lies with Arcana RPG, or at least how it interacts with one or both of the other two.