The biggest blocker for me is having confidence my output renders the same with people using MS Office, pdf output isn't always sufficient.

That has been a lot less of a problem lately. Why not try again and open a bug report if there's an issue?

Because there’s no one and done testing for it. You need to check every document you make with Office (so you’re paying for Office anyway…) to ensure it’s correct.

All very well for an open source software project but for software you’re using day to day to achieve other, business central, goals, it’s a lot of lost time with little benefit.

> for software you’re using day to day to achieve other, business central, goals...

...you should use something which is reliable, no more complicated than needed for the purpose, which assures documents made now can be read in the distant future, keeps your confidential information out of the wrong hands and which is sure to be available to anyone who needs to have access to it.

Doesn't really sound like Microsoft Office is a good fit if you ask me.

You want to use the same stuff your clients use, that’s guaranteed to look the same on their computer. So Office it is.

Well, you want to be using what your clients can read, it doesn't have to the the same software. This is true for most file formats - audio, video, image/graphics (the latter more restricted due to other entrenched proprietary formats) - but the 'office' space (no pun intended) is still suffering from decades of abuse of its position os operating system vendor by Microsoft. Windows is only getting worse with every release so it is just smart business sense to steer away from it and things depending on it. Microsoft Office is one of the few remaining reasons often quoted for staying with this deteriorating platform so there are other incentives to move away from it. The best moment for moving away from Windows was years - or decades - ago. The second best moment is now.

When is a PDF not sufficient? I write all my reports/letters in LaTeX and if someone complained about receiving a PDF, I would send them the source and wish them good luck.

That is actually why I got into LaTeX in the first place!

My resume was initially done with LibreOffice and I'd send recruiters a PDF, and they would ask for a .docx, and when I would send that they would screw up all the formatting by inserting their ugly logo on the top.

When I "ported" my resume over to LaTeX, I would send the PDF and they'd ask for a .docx, I would say "Oh, the resume is done in LaTeX. Here's a link to the source and instructions on how to compile it, feel free to do what you need".

Then they would just submit the raw PDF.

..or they would just not submit it at all.

As far as I am aware that never happened. Every time this particular situation has happened, I have gotten a callback.

When I need other people to continue editing it.

I also prefer LaTeX, I've written hundreds of letters, multiple papers, a few thesis and my CV (maintained for the last ~20 years). But the defacto for business documents sadly isn't LaTeX.

As long as that is the goal Microsoft can block uptake of any competitor simply by making sure that is never achieved. They have a lot of history with this - DOS ain't done 'till 1-2-3 won't run etc. - so you can rest assured that they'll do it again. Maybe you should change your output so it isn't as reliant on 'rendering the same', i.e. make it less complex and with that less easy for Microsoft to claim the error lies with the other party? Word is not a DTP package nor a typesetter, it is a document editor. Fancy layout has never been the forte of this class of programs, they're meant to make sure the output works on different computers, different printers, different monitors.