Yes, the game is difficult. The higher end wyverns and elder dragons will 1-hit KO you if you aren't geared right. And while you can play the game solo, it's really about the co-op aspect. 2 to 4 player teams working together to take down massive bosses.
The game takes practice. You need to know the best way to use your weapon of choice (of which there are many). You need to know the weaknesses of the enemy you are facing and exploit them. Each enemy has an elemental weakness. They have weak points on their body. They give tells as to what they're going to do next. They have special attacks that can be avoided if you are good at dodging/rolling.
It's not an action game that you pick up and do ultra combos with right off the bat. It's an investment of sorts. There are no levels to grind out, but a big portion of the game is hunting down materials to build better armor and weapons. In the end, you really need to experience it for yourself, but I highly recommend doing ALL the weapon training tutorials. Play it with others. If you try to solo everything, you will likely get frustrated and quit.
It's an excellent franchise, but like a deep fighter, you have to invest time in learning the game to see a payoff.