I'll beg to differ. I've been running my own email for almost two decades and although the environment has changed, it is still perfectly accommodating of small operators that keep themselves up-to-date with context (e.g dnswl listing, notifications to major recipients, signed headers, best practise DNS records etc etc).

I changed IP address in the last 18 months and despite great trepidation, was pleasantly surprised that deliverability was not degraded.

Paying a bond feels like protection money for something I think my domains/hosts already have: a good reputation.