Hi there!
Normally I would represent OOPS Inc, newly formed casual guild with an active discord and quite a happy, lively bunch of people.
But having been in your shoes when I was working at a sorting center for UPS, I feel your pain of playing by yourself. And I’d be remiss if I didn’t try to help out a little bit.
First up!
After Hours
The guild’s name kinda says enough.
They’re progressing through Mythic, but I doubt they’ll reject some one who’s less interested in raiding and more in just hanging out.
The Audacity
It feels weird promoting them, cause I didn’t exactly leave on good terms a couple of months ago. But they are a friendly bunch of people and were usually doing dungeons from around 21:00 past midnight.
Talk to Baiou, the guild’s leader first. She’s an odd one, but if you can get along with her, you’ll have a great time there.
Temporary Solution
They raid until the time you log in. And there will usually be people around after the raiding ended, that want to do a couple of dungeons or just hang around.
Aaand last but not certainly not least (I would know, I"m still in it!)
OOPS Inc
We’re a casual guild that is still very much forming, and though there’s less activity around the hours you play, I log off around 22:00 and there’s always still people online when I do.
I can’t guarantee you’ll have people every day. To be fair, I doubt any guild can guarantee that, unless it’s one of those 500 people monstrosities where no one talks or knows eachother. 
That’s all the info I have for you regarding guilds that might suit you. If none of these are to your taste, I sincerely hope the right one gets in touch with you soon.
Good luck out there, nightowl!