Subtitles are an essential aid just as clear speaking is, the problem is two-fold, (1) learning issues within the deaf community, and (2) misguided opposition to acquiring literacy in the host country language, via 'rights'. If ignorance is a right, a real step backwards.
I am not aware of Polish sign language, but do know the British version lacks considerable detail live, and provide 'highlights' more than anything else. Which isn't really serving the deaf to follow the depth of information neither is lack of support to read etc. Covid e.g. in the Uk has a barrage of depth and detail being distributed 24/7 for over a year, hearing struggle to follow the technical/data-driven, and political detail, via BSL the deaf get little or nothing from it except an 'image' deaf sign but national broadcasting via an interpreter is pretty simplistic and basic because there is no time to explain any depth and terps have to appeal to the ablest deaf.
Sign CANNOT replace what they need to understand via depth. Current political updates e.g. on covid tell deaf next to nothing, except the most simple of explanations. To get detail they need to read hence the essential of captions etc. Most deaf bypass sign when titles come up, so this tends to suggest the titles is better access than the sign is for them. The sign becomes an 'assist' just like lip-reading does. It's a social tool, it's not an academic one despite claims, and lacks 90% of essential signs to progress as such.
We'd like to see clear lip-SPEAKING as well as sign, but titling helps no lip-reader to follow in that respect, we are a text society, yet during covid this last 14 months, deaf demanded lip-reading access and insisted on clear masks to do it despite poor abilities in the signing world to use it, they knew sign wasn't an issue. We could suggest this video is merely a 'plug' for sign use and not an awareness vid for inclusion since it omits a number of essential 'assists' deaf and HoH need to follow effectively. For those deaf who oppose host languages in preference for their limited own and grammar, then this is simply making a rod for their own back and thankfully, young deaf are not buying into this negativity and relying on titles as well which has effectively replaced sign and lip-reading really on visuals.
This is the real concern of the cultural deaf and why they lobby against text usages and local languages because it will replace what they use. The bottom line is access, and so deaf have to take what they need to get that not put up barriers to it. We aren't going to end up with 3 or 4 modes on a screen or some sort of biased pick n mix system. In the UK we call many of these sign campaigns the 'Canute Syndrome' in that they feel they can actually replace their idea of access to replace all others deaf need to use also.