Yes, disappointing. On July 26th, someone posted an update in the Atlassian Community on this topic. The user heard from their Atlassian/Trello support tech and they said
"Our partnerships team have gotten in touch with Microsoft on our end and are asking them to fix this issue. Unfortunately we can't promise that the issue will get fixed as this lies solely with Microsoft, and we do not have any sort of timeline or ETA. I'm sorry, this probably isn't what you want to hear!
Our recommendation is that instead of relying on a fix here from Microsoft, is that you pivot over to using our email to board feature native to Trello, which we support. Essentially, you can generate a unique email address for each of your boards, and from Outlook or any other email provider, you can send emails to this address and they'll turn into cards on your board. I'm not sure if this has the exact same functionality as the Outlook add-in, but should help you in the interim and also supports sending email attachments to cards which is the broken functionality in the Outlook add-in. We have an extensive help doc about this feature at https://support.atlassian.com/trello/docs/creating-cards-by-email/
If you do want to continue using the Outlook add-in, I'd recommend continuing to email Microsoft until they work on the fix, like we will do on our side. Again, I can't promise that Microsoft will fix the issue or will even reply, but we are asking them to fix the issue on their end. We have had reports of the Outlook add-in support email engineers saying that it is with us to fix - this is not the case and we are urging Microsoft to look into the issue."
This is such a great integration between the two services and it is disappointing Microsoft is not responding to email reports on it.