I don't watch through a web browser so can't say but with the built in TV apps the quality is pretty damn good.I may have missed some better recent content as I'm fairly selective what I watch on Disney plus - but on my Philips 436M6 QD-LED VA there are tons of artefacts or blockiness in dark colours, parts of the image which are noticeably lower resolution or visually noisy, etc. I don't have it with UHD Blu-ray and decently produced 4K stuff on YouTube is acceptable.
The piracy concerns are pretty LOL as it is so easy to circumvent in this day and age (as I've mentioned before probably one of the reasons there is a push to try and get TPM adopted as it is a component in taking more control on something like that - though won't stop people being able to use capture cards externally).
Gave up on having a HTPC years ago, too much hassle compared to a cheap streaming stick.