IIUC, what is causing the problem is Windows-11.
AFAIK, installing MSXML SP2 rather than SP3 with the security patch and "SDK Parser" update ...would be 'asking for trouble':
https://www.google.com/search?q=MSX...MIHBTMtMi40yAeJAQ&sclient=mobile-gws-wiz-serp
https://www.catalog.update.microsoft.com/Search.aspx?q=MSXML 4.0 Service Pack 3
https://www.google.com/search?q=MSX...RwgcFMy03LjXIB-QB&sclient=mobile-gws-wiz-serp
MS is aggressively seeking to eradicate use of Windows-10 like they did with Windows-XP when they foisted Windows Vista on the computer world (Vista was ultimately declared an 8 Billion dollar 'mistake' by some).
And MS did the same with Windows-7 when they launched Windows-10.
Thus, we see IMHO, un-necessary deprecation of Windows-10 in general, termination and/or hiding of download links for numerous essential system components such as MSXML 4.0 SP3 which can still be used in "Compatibility" mode (with- or without- applied security patches released last year, or only or a few years ago) while installed on Windows-11.
The links are supplied for download of MSXML 4.0 SP3 because ADE AFAIK, has version-specific dependencies on that code component of XML in Windows due to its associated dependency of the BGLComp SDK compiler in FS2004 through FSX SP2 (and IIRC, some versions of P3D).
IIUC, MSXML 6.0 SP3 can
not be substituted for MSXML 4.O SP3 with legacy versions of the FS SDK.
You may note that I am not thus far, suggesting end users who still base their activities in "legacy" versions of FS9 etc. are 'asking for trouble' by using those older version, nor that their potential for problems may be substantially increased if they begin using Windows-11.
But, honestly, based on what I see taking place with MS via their 'Draconian' BS with the Windows-11 / UEFI / TPM Module agenda being further subserved by their escalation of interference with legacy core components by their Security and anti-viral software, I am increasingly compelled to point out that FS users may wish to download and install Windows-10 (from .ISO's that are still available even today on MS' own servers), and disable MS security software, substituting instead, Malwarebytes payware edition with Rootkit Protection, and Malwarebytes AdwCleaner as needed.
I hope this helps explain my having posted the info I did early this morning before my daily coffee.
If I have missed something here, please do let me know.
On second thought, I am just going to say it now ...IMHO, Windows-11 and MS Security software (even if running in Windows-10), ultimately is more likely going to cause trouble eventually for all versions of FS older than MSFS 2020.
GaryGB