Protonmail and now wanting to have attachments downloaded what?!

I have been using proton - protonmail for many years and liked it until they did a revamp and changed the interface a few weeks back. I never had any issues w their email service at all. Last night I got ready to send a M/S Word doc as an attachment in the email, something I have been doing for 30 yrs. It would not send the doc and it tried to download my Word Doc to their pop up window telling me to download the doc. I have never had an email program want to take over an attachment or be in the middle of that process. I am confused. Have I gone insane and lost it? I am very confused. I emailed them and their answer is below -
Please be informed that you can only preview PDF, TXT, JPG, and PNG files without downloading them on ProtonMail. If you click on the attachment of any above files, the preview window should pop up automatically.

So now another "provider" wants to be in the middle of my emails? I thought email was a service to send and receive like the mailman.

Please note that if the files are Microsoft Word documents (.doc or .docx), unfortunately, we have not implemented a preview function for these files yet.

You will need to download these files on your device and then open them with the appropriate application.
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I read your site as a very non tech person - I try to figure stuff out but what the heck is going on now?

I sent the email to someone and it was there but they were not able to view the doc, the doc but not visible and told them to download .........WHAT is going on? Help thanks I don't use Protons Cloud and don't want to. My device is my trusty desktop. I have made no s/w changes of any kind.