There's always someone mis-using it, and the same applies to every other platform. There's always someone hijacking forum threads, or asking questions in comments instead of starting a new topic. None of this is exclusive to email.
For hackerspaces, tech meetups, book clubs, cycling clubs, city cleanup volunteer groups…
It works fine.
Don’t let your bad experience ruin it for everyone. Especially with an administrative backend, email-based distribution and comms works great for smaller groups!
But because subject lines are more work and people who love sending email tend to love it because it is very low effort, the venn of email senders and those who write subject lines is small.
(¹yes, it seems like you can work around it by going to the URL de novo, … but IDK, doesn't seem worth it.)