I'm connected via LAN cable directly to the Hughes modem with my smart TV. I can't stream a movie without it buffering every 1 minute. This has never worked with my TV apps or my DishTV apps. I would think via wired connection it works work. I had the modern replaced recently because wifi was useless on the last one.
I have Chromecast on an older smart TV and if I use my mobile phone to cast to my TV it's way better streaming.
Why is it so bad connected directly to the modem?
It's congestion and latency. Both happen with satellite internet, more so during prime time. If you want to watch TV, your best bet is satellite TV. That doesn't have any issues and uses no data.
A couple of things you can try are snoozing or turning off the Video Data Saver and/or reducing the resolution of the streamed content, whether at the source or locally.
Unfortunately though, as maratsade intimated, the combination of congestion and high latency can make streaming somewhat difficult.
As an alternative, if streaming movies and or TV shows is important, something you may want to look into is PlayOn Cloud. It's almost as if it's specifically made for ISPs like HughesNet, where data is precious and streaming doesn't always work well. It's a service where you set up the item you want to stream, they stream it for you and record it on their cloud based DVR, and then they convert it to an mp4 file. You can then download it and watch it on the device you downloaded it to, or you can copy the item onto a USB flash drive or external HDD/SSD in order to watch it on a Smart TV, or even from a DVD or Blu Ray player that has a USB port for input. Many of the big streaming services are supported, like Netflix, Hulu, Amazon Prime, HBO Max, etc. They have plans, but I just buy the credits and use them piecemeal. The only drawback to not having a monthly plan is that the items are purged from their servers after seven days, so you have to download them within that time. What you download is yours to keep forever and watch as many times as you like. And there's no buffering, as you're watching from an already downloaded file. The PlayOn Cloud app requires an Android or Apple based device, though I've read of people running it from a Windows computer using an Android emulator.
Anyway, it's just a thought. If you have any questions about PlayOn Cloud, feel free to ask. I've been using it for over two years now, and it works well. Well over 100 movies and a number of TV series so far. Maratsade uses it too.