Welcome to Zorin OS!
Never forget: people that make a living (or a profit) out of creating content for YouTube or any other similar platform supported by ads, have an incentive to exaggerate everything in the name of higher view counts.
Ubuntu's LTS releases are supported for 5 years, which means that Zorin OS 17 will be supported until 2027, so there's no problem about security in that regard. But it is true that some programs may not be available for download or install at their most recent versions because of this. If you find that certain features are absolutely essential and need them then this will be a problem for you.
However, there is something called "shiny new thing syndrome", and it does have a big impact on people. I encourage you to try Zorin OS without thinking about what version are your programs running on. Chances are you won't even notice anything missing. Make sure that you need the latest before growing desperate because the grass is greener on the other side (supposedly).
Feel free to ask any questions if you have any!