I solo just about all the time (and not because I'm part of the 'new generation of players'; I started gaming on an Apple ][e, and it has been long and long since I played a console game ).
If you think soloing doesn't require at least as much tactics and strategy as grouping, I'm somewhat bemused. I grant that grouping may require more patience, particularly with the cat-herding that raids can become But part of the game for me is character design. Do I give up a capstone and spend two levels to gain Evasion? Do I take a level in Druid or Artificer so I have an extra lever puller? A level in Artificer or Rogue, and push my Int at the expense of other scores, so that I have enough cross-class skill points to be a competent trapper? What's the return on pushing the Short Sword linear with Kensei, Warpriest and Drow enhancements? (+12 to hit and damage and +1 to threat range seems nice, although I haven't even looked into whether they stack yet) There's plenty of strategy involved before you even set foot in an adventure.