In-game chat is so limited and tedious to use that I would not consider joining any guild that doesn't have a discord server and require all members to join it.
I was briefly a TB officer for a guild that didn't require all members to use discord. Had a guy go rogue and star a zone we were supposed to only preload. He then waited 9 hours to bother asking why commands on the TB map said to stop all action in the zone he took over the star threshold. I DM'd him in-game because he wasn't on discord. He joined the chat, so presumably saw the messages I sent, but never bothered replying. Not even a "shove off, poohead". Just no reply at all.
If I had been the Guild Leader, that guy would get kicked from the guild immediately after TB.