If you have any experience in similar genre games then the complexity is really not too bad, a lot of the old recipes have been simplified and that helps considerably.
The best way i find to describe the combat would be ‘dark souls light’ you have a decent variety of weapons but they all function more or less the same way, light combo, heavy combo, block or special attack plus you get a few ranged options as well.
DLC is very much optional, only siptah adds new content that being the new map and rhino saddles, the other DLC is decorative or aesthetic. Anything added by normal DLC be it armour, weapons or building pieces has a base game counterpart with the same stats, with very few exceptions notably the derketo building pieces and the aforementioned rhino saddles.
As for general difficulty, once you’ve got the basics down it smooths out, it can seem tough at the very start when you are at your weakest, but providing you don’t explore too far to the north until you have better equipment you should be fine, additionally if you avoid any massive looking creatures and try not to fight big groups in one go then most of the time it is pretty easy.
Once you know what you’re doing, the game is easier now than it has ever been (too easy in my opinion), but it still does very little hand-holding for new players. You will either have to exert actual effort to learn this game, or find people to answer questions. But because PVE in particular is so brainlessly easy now, you are likely to find bored people willing to hand out all the shortcuts. That’s not how I recommend learning to play, but if you’re afraid of being challenged there will probably be people willing to help you sidestep challenges.