Both services are trash. Maillgun in particular holds emails even for days and reports them as sent. Apparently it's a "security" feature.
If there is a security related issue on the receiver side (like an expired certificate), the sender (Mailgun) may hold the email and retry a couple of times. Eventually the issue may get resolved and the email will be delivered, or the sender may choose to deliver the email without encryption (unless MTA-STS is used, of course). During this whole process the email is sent, but not delivered.
I understand that the status 'sent' may be confusing to you, but calling the companies 'trash' just because the email protocol from 1982 does not uphold your standards is a bit harsh.