I've been operating my own mail server on the same IP for the last 10 years, so not as long as yours and I also don't have problems. I also disagree with one of the parent comments that you will never know what happens to email: Gmail supports DMARC, and will give you stats and tell you what happens. You can also sign up to various sender services and domain whitelist sites and so on. I've also seen mail providers do fun things like 'permanently defer' email as a means of blocking and this actually notifies you, albeit in a disruptive way, by leaving the email permanently in your outgoing queue.

I do agree however IP reputation matters. If you share an IP with other hosters, or your IP has been recycled from a bad reputation IP, or you have a residential IP or have found your way onto any of the email spam lists recently, or been reported for abuse or marked as spam enough times by freemail service users, you may have trouble getting to 'inbox' and eventually even getting delivered. Reporting systems like DMARC should let you know, however, before it becomes serious.

I don't think running your own email is a high maintenance activity that some suggest (especially for small servers) but it is definitely more effort than outsourcing it to someone else. I'm glad services like this exist, if only to prevent email becoming a Microsoft-Google walled garden.