I work in the email industry, so I might be a bit biased on this one, but in my experience self-hosting email has actually gotten better, or at least for the outbound part, funnily enough. But I won't go into why IP-reputation is a thing of the past, for the risk of having to write a very long post that'll be downvoted anyway.

The biggest problem that I personally see with self-hosting, email in particular, is that most resources you find online are outdated, based on superstition, or simply plain wrong. There is a lot of heated debate around running email services, and many bitter comments from people who tried once and got burned.

Self-hosting a personal email service, or any kind of service for that matter, isn't impossible. The internet is still based on free and open standards (the RFCs). But it is free like speech, not beer. Running your own services will cost you resources. Most of which is your time, but some may also be money (for example: ML-capable hardware, certificates, licenses, etc.).

You'll have to be willing to learn, and more importantly: willing to accept that it is a lot of work to setup and maintain any self-hosted services, not just email. You have got to be willing to read through the RFCs, study the errata, read the documentation of your software, be willing to spend time in configurations, being sure you understand your settings, set up lab environments to study both ends of the service (for example: the inbound and outbound service in an email transaction).

Self-hosting is a great learning experience, a fun hobby even if you enjoy such things. It'll allow you to explore all sorts of tech throughout the entire networking stack. But due to the amount of work it takes to setup and maintain, it'll never make financial sense to self-host, at least not in a professional setting. Cloud-hosted solutions, email being a good example in particular, have the benefit of scale: they are dirt-cheap and work really well. It makes zero financial sense to self-host any email service beyond personal use. Unless hosting is your core business, don't be tempted to self-host anything, focus on your actual business instead.