Yes- LTWOO quality does appear to be low. But a few observations of the video review.
The reviewer compares them to Shimano 105 but I think the better comparison is Campagnolo as the shifting is similar. On Campy's lower end shifters (Powershift) you can only shift one gear per lever push vs 3 on the higher (Ultrashift) levers so the LTWOO's 2 per shift is reasonable.
Campagnolo also makes the small lever from plastic and they seem to be OK so there's no reason to believe the design is fundamentally flawed. His other criticism is there is no way to know if you're in the last gear, but Campy also works like this and few people seem bothered by it.
But overall, I'd give them a try if I was looking to build a cheap beater - I'd just make sure the clamping screws had a washer.

EDIT: Campy powershift is one upshift (thumb lever) per push vs 3 on Ultrashift and 1 on LTWOO. Downshift (lever behind brake) is 3 per shift on Powershift, 5 on Ultrashift and 2 on LTWOO.