I feel like it's extremely poor design to force individuals to pay for a product which they only have digital access to. At least provide a way to download purchased content. The idea of paying money to not even own anything and the risk of everything being shut down, account lost, etc. and losing what you have purchased is ridiculous and needs to be addressed. I hope I'm not the only one who feels this way. Ended up having to buy a physical copy of a rulebook after discovering I couldn't download my content from DnD beyond.  

I feel like it's extremely poor design to force individuals to pay for a product which they only have digital access to

A digital only service will be a digital only service. If you want something tangible then get the physical book. This isn't a D&D Beyond thing, it's a "how digital services work" thing. When you buy a movie on Amazon Prime, it's a digital thing and if Amazon Prime ever goes away so does what you bought. This is very normal and common. 

At least provide a way to download purchased content. 

They did. Get the app, download and use offline for as long as you want. 

The idea of paying money to not even own anything and the risk of everything being shut down, account lost, etc. and losing what you have purchased is ridiculous and needs to be addressed. 

It's the nature of almost all digital services across the whole internet. The reason is reduced piracy, more control, and future security for the company. Sure, it's not so great for the customer, but it is for the business and they want all the security they can for their bottom line. This is why it's the global standard.

Ended up having to buy a physical copy of a rulebook after discovering I couldn't download my content from DnD beyond.

As mentioned, you can download it. But anyway, if you want the ease of digital convenience - get digital, if you want future security get physical.