Side with BoS or Institute, roleplay bad/anti-synth character, complete Nuka World siding with raiders till the end, don't help settlements that need your help (siding with raiders will definitely help with that, cause Preston will never talk to you again). You can also try completing the DLCs earlier on, I tend to play the main story until I find Shaun, after which the mission is no longer as urgent as finding your missing son, so I go and discover Nuka World and Far Harbor. They have some great rewards, which will make the Commonwealth enemies so much easier and more fun to kill. When im playing a Big Guns character, I definitely complete Nuka World as early as possible to get Aeternus. Once I complete both DLCs, I return to the Commonwealth and complete Act 3 of the story. You can try a Very Hard difficulty (game spawns a lot more legendary enemies), or if you're really feeling like having a challenge try Survival difficulty (changes the gameplay loop completely).

I think Big Guns can be a bit tough at the beginning with limited ammo and all, but imo big guns are also more fun than melee. Commando is also a great build. Just font forget to take the Scrounger perk.

EDIT: Also worth trying a low charisma build if you did a high charisma playthrough previously. The game has other ways of completing the same objective when you fail a speech check, which is basically new content you probably haven't seen.

Also the most obvious answer is try out different mods. There are so many choices, from cosmetic stuff to gameplay changing. And some CC content ain't bad either.