> they used whatsapp for coordination so I didn't join

How much personal opportunity cost is acceptable before it becomes worth using a platform you don't like...?

Remember that even if it your life's sole goal to eliminate the use of that platform worldwide, you will probably achieve more if you take every opportunity possible, including those gatekept by the platform you don't like...

I wouldn't have been able to attend so it was futile to install whatsapp and join the discussion.

There is no ideological reason behind it.

Then you wrote your original message in a very odd way, implying it was because of the WhatsApp use that you did not join. Not harping on you, just an FYI in case you're learning the language or would like to increase communication skills.

They're probably communicating on whatsapp.