itch limit the size of files they will distribute via their servers, hence many devs split the archive.
You can get a bigger allowance but there is still a limit.
Rar or 7Zip is as valid a format as any if you have the apropreate software installed. Most OSs do support the old 1980s format PKZIP, but in the decades since we have moved on so the files can be smaller by a huge margin, and in the case of RAR also include a recovery record so corrupt downloads can be rebuilt.
I even use Rar files with Amiga OS (a 90s computer) because it is so widely supported and used.
My solution would be make the distro as a multipart SFX-RAR, so all you have to do is double-click the exe and let it unpack itself.
Or simply advise users that this is a multipart RAR archive so you need to have Winrar, Winzip or 7zip etc. installed to unpack it (all are free and small).