Oh, yeah, it's definitely possible to put Roku on hardware that's so incredibly shit that it runs poorly. And Roku's software (like everyone else's) has definitely been bloating for a long time. I discovered that when I bought a Hisense, because I needed a new TV and Costco didn't sell the previous brand of dirt-cheap Chinese Roku TV I'd bought before. God damn did that brand cheap out, the other brand's older TV that cost the same performed so much better. It even crashed sometimes, seemingly from OOM-like pressure, which I'd never once seen happen on the older one.
But it's also the case that decently-performing Roku devices exist running on hardware that surely wouldn't do very well if its "apps" were Webtech-based. JavaScript, sure, that could probably be brought in (and would surely be an improvement over BrightScript, as far as dev-ex) but a whole browser engine? Nah, they'd have to greatly increase their min specs, and their whole niche is "runs twice as well as Android-based TV UIs, on half the hardware".
But it's also the case that decently-performing Roku devices exist running on hardware that surely wouldn't do very well if its "apps" were Webtech-based. JavaScript, sure, that could probably be brought in (and would surely be an improvement over BrightScript, as far as dev-ex) but a whole browser engine? Nah, they'd have to greatly increase their min specs, and their whole niche is "runs twice as well as Android-based TV UIs, on half the hardware".