So this is the first time DLC has been released for a Pokemon game, and it was not something I was particularly looking forward and to be perfectly honest I was not going to buy until I saw the Pokemon you get because of the DLC and thought he was really cute so I had to have.
The Isle of Armor DLC allows you to visit a whole brand new Island as well as get an addition to your Pokedex. This means there is even more pokemon to catch, some previously not available without the new DLC. Not only that but we get new Galar forms with the slowpoke line. You also get about another 5-10 hour worth of gameplay from the dlc which to some people might be a good thing.
For me it was great to see some more old Pokemon in this new generational style as it is the best Pokemon has ever looked. Plus having the new legendary be given to you is always a plus. I do really like the journey that you have to go on to be able to evolve this legendary as well (even if it does involve an almost 60+ level grind).
The DLC costs £27 from the eshop which is a lot of money for a dlc to a game that already costs £60 but you do get the new upcoming dlc coming out some time this year as well but that is still £13.50 for a dlc where you really only get an extra 10 hours worth of play time and a lot of that is grinding. So for me unless the new DLC comes out with something amazing and adds at least another 10-15 hours worth of story then I personally dont think it is ever going to be worth the money. Hoping Crown Tundra is a lot better.