If "newer = better" was my thinking, I'd be all for these new protocols on top of JMAP. But I actually think they're useful only in a limited context.
JMAP is better than IMAP because IMAP is a too stateful design, the IMAP/SMTP distinction allows for misconfigurations where sending doesn't work, has dozens of extensions where key extensions are inconsistently supported, doesn't have as many batched operations, etc. One could make an effort to improve IMAP - but the effort to do this consistently in server software would likely be comparable to adding JMAP and the result worse...
OTOH, the new protocols intrude on areas that go far beyond email software (you're very unlikely to get support for these in older Androids/iOS/Windows even if the modern OSs ever consider them), and don't offer as much as JMAP offers over IMAP. The cost/benefit is worse. They may make sense for a JMAP email client but IMHO not elsewhere.
JMAP is better than IMAP because IMAP is a too stateful design, the IMAP/SMTP distinction allows for misconfigurations where sending doesn't work, has dozens of extensions where key extensions are inconsistently supported, doesn't have as many batched operations, etc. One could make an effort to improve IMAP - but the effort to do this consistently in server software would likely be comparable to adding JMAP and the result worse...
OTOH, the new protocols intrude on areas that go far beyond email software (you're very unlikely to get support for these in older Androids/iOS/Windows even if the modern OSs ever consider them), and don't offer as much as JMAP offers over IMAP. The cost/benefit is worse. They may make sense for a JMAP email client but IMHO not elsewhere.