The folk that write code for Smart TVs are not that plentiful and when this began the makers were all over the map without a standard OS and design. The result was predictable. And yes, a Roku is the better solution.
Just found this Vizio support page listing the Vizio models the Hulu Plus app STOPPED working on. https://support.vizio.com/s/article/Hulu-Plus-no-longer-working .
There are similar complaints for Samsung models.
Symptoms: Vizio TV logged me out of Hulu Plus app. When you try to get back in, it never displays the device activation code, just "Loading...". If you choose "Log into Hulu Plus" it just sits at "Waiting" once you enter the userid/password, no matter how long you leave it trying.
Netflix/Amazon/YouTube/etc built-in apps all connect to the internet and stream just fine.
After calling Vizio and uninstalling the Hulu Plus app then re-installing/unplugging and waiting 60 seconds while holding some button/playing with DNS settings/resetting the TV to factory/(etc) to no avail, called Hulu support. The first time I called, we went thru many the same gyrations as with Vizio support and there was no fix. The second time I called, Hulu acknowledged a known issue with the Hulu app on some smart tv models, Samsung included, and gave me a month's credit.
After calling Hulu support again yesterday, they elaborated that there are Vizio models that cannot take the upgraded Vizio app and the built-in app version will simply no longer work. Got another month's credit, but now there is no hope it is going to get fixed. They suggest getting a Roku like device or getting to Hulu Plus thru an Xbox or Blu-ray attached to the Vizio.
I don't know who I'm pissed at more, Hulu for cutting off the old app or Vizio for not being able to upgrade to the new one. My XVT553SV is only 5 years old. You still see them for sale new on the Internet. What does that say for buying any smart tv with a built-in app?
If I were you I'd definitely call Hulu and report your dis-satisfaction and ask for a credit if they don't offer one. Log into Hulu Plus, in the top right window pick Help, then Contact Us, then troubleshooting. On the left, put in your phone number and they will call you back.