I don't know if this is my personal experience alone, but I feel that open source spam filters like spamassassin and rspamd do a much better job than gmail's filter. Gmail's filter has too many false positives and false negatives. We shouldn't give up on email just because gmail is bad at it.

Besides, I feel that gmail and most other webmail providers have created a bad usage pattern for email. Email is much more pleasant when used with an indexing tool (notmuch/mu), custom filters (sieve) and a proper spam filter. Custom domain with dedicated account (or alias) for development also improves the situation.