DTV's hardware does look increasingly dated, especially with regard to its lack of streaming apps compared to current offerings from DISH, Comcast Xfinity, etc. I guess it's possible the new company invests money to bring out a new generation of DTV receivers with popular apps but that seems unlikely. Because if a customer wants streaming apps, it means he has broadband. And if he has broadband, well, they already have a solution for you in the form of AT&T TV (or whatever the new DirecTV company renames it to), which has a custom box with voice remote, Google Assistant built in, and access to tons of Android TV apps. And pretty much the same channel packages as DTV, but cheaper.
Only way I could see them bringing apps to DTV is if they made the AT&T TV Android TV box work as a client receiver in conjunction with a DBS server like the HS17 (i.e. Genie 2). In fact, language in the original user manual submitted to the FCC with the AT&T TV box a few years ago suggested that that may have been the plan.
I think it's simply that by the time there was a real need for streaming apps on DTV receivers, AT&T had bought the company. And their long-term master plan from the get-go was to essentially blend DTV and Uverse TV together into something that would work over any internet connection -- what would ultimately come to market (with simpler hardware and much later than originally anticipated) as AT&T TV. Read this article from way back in 2015, just after AT&T bought DTV:
AT&T said it plans to stop investing in its U-verse CPE platform and will instead use a "derivative" of DirecTV's in-home equipment to create a new, in-home TV product that the company said will display content from AT&T and others. The company also said users would be able to access the same...
I think AT&T's plans had always been to shift their viewers toward the internet. I just don't think they saw the need to bring out a new generation of DBS-only hardware with apps, or to try to get apps on DTV receivers like the HR44, HR54 or C61.