I had a complete blast with 5, and so did my son. We played the living crap out of it.
It is also extensively modded, ala Battletech, so even without DLCs you can add a serious amount of depth and breadth to the game as you like.
When you get the twin gauss Clan mech at the end of the vanilla campaign, you know you want more of this.
Edit - there is a Youtuber named Baradul who has a ton of Battletech and Mechwarrior 5 videos showcasing various mods and campaigns if you are wondering if you will like any of it.