I thought this video was awkward, not sure how relevant it is compared to todays modern way of speaking japanese.
Nonetheless, you should look for recent materials as well.
I've just watched the beginning of this video. Here are my quick impressions:
- It seems to have been in the late 1970s or the early 1980s. That is to say, it seems to have been about 30 to 40 years ago.
- There isn't much difference between the words and phrases at that time and in recent days.
- The way of talking and the gestures in the video feel slightly old-fashioned. I don't think that is because of their clothes and hairstyles.
- A lot of elder people are still talking this way.
So, I think it is completely all right to learn phrases and sencentes from this video. If you can talk exactly like the people from the video, you look mature or a bit old-fashioned, but I don't think that is a bad thing. I think it is a comfortable way of talking to a lot of native speakers.
I'm still learning Japanese, but as far as I know through reading about English, my own language, I don't think that language evolves so rapidly as to be so different from only 20 years ago.
The main things that could have changed between now and then are probably small. In American English, it's probably the slang that has changed the most, and perhaps some kinds of casual speech have been more recognized as normal and acceptable rather than looked down upon as uncultured...(that second part's just my opinion).
In Japanese, I would expect the slang and the "cool" words that kids use nowadays to have changed, just like any language.
If you're really interested in the ways in which Japanese language is evolving, I bet you could find some info with a google search!