Why is theta ranked so low?

Very good question. Maybe some alumnae might want to give a historical overview?

No sorority is top tier at every single school they're at. Theta is no different

In my opinion, I think it just boils down to the fact that every house needs a place in the ranks. Theta is a strong house that would otherwise be a top house at different schools... but Greek life at Bama is extremely competitive and Theta just kind of fades in the background with other houses here... not every house can be top.

They aren't part of the machine so that's definitely part of it, gphi joined the machine and grew so maybe theta should take the lead

Theta just for their new mansion and moved into it 3ish years ago. Before the new house, they had a hard time recruiting.
Since having the mansion, they have done really well during recruitment and have recruited cute, social girls in the last 2 new member classes. You see Thetas at a lot of parties and date parties now way more than in the past. I have no idea why all the Theta hate on GR but they are a rising NR house for sure.

For OOR PNMs, I don’t think they are ranked low. For Southern girls they aren’t a popular house yet because they are so new and just go their big house.