FormerlyHemlock
Hero
He does, and that is what he does. But... that's his first order strategy (stand as far as possible away (in this case 5 ft) and shoot).
Generally the problem with switching to other weapons is that while he's got a rapier and, I think, Duelist fighting style, his golfbag weapons are not as good as his primary weapons so he needs to be eating a fairly huge disadvantage from something for 'and I shoot it with my crossbow' not to be the go to attack.
Let's say then, based on what you describe, that he's got four main attack modes:
(1) Shoot with crossbow for damage (with or without Sharpshooter sniping)
(2) Shoot with crossbow for disarm (using DMG Disarm option, opposed attack roll vs. enemy Athletics)
(3) Throw net to restrain
(4) Rapier and shield for damage
Granted that, given crossbow expert, #4 is probably not useful very often. But #1, #2, and #3 have very different utility profiles, e.g. #2 is more likely to be useful vs. Frost Giants than #1, and #3 is more useful in a large party. Sure, it's true that 5E is so easy by default that you can probably get by on just #1--but you don't have to play on default difficulty. I strongly recommend turning up difficulty to somewhere between Deadly and Quadruple-Deadly if you want to have interesting fights. Or in other words, see if you can get your DM to handwave fights under that threshold ("You kill the bugbears, losing 3d6 HP or one spell slot in the process." "[rolls] Okay, I lose 8 HP. What happens next? Can I tell if anyone heard the struggle?") and only break out the initiative/battlegrids/etc. for fights that you could actually lose. You ask the question, "Why would I choose to play a mostly-noncombat-oriented campaign in D&D?" and the answer is, "If you want the potential for violence to shape the campaign." If the Parshendi invasion could theoretically be resolved by fighting your way across the continent, infiltrating the court, and butchering the Parshendi Emperor, but you can't do that because you're not a demigod and you have to sneak around and do what you can while looking for opportunities to do more... then D&D might be a good ruleset to use for the campaign. If on the other hand the campaign is about legal maneuverings and love triangles and looming bankruptcies, maybe GURPS would be a better choice.
We've played together over a ton of different game systems. I think a huge part of it is 5E. Obviously everyone can disagree about what constitutes good encounter design for someone's home game, so let's bust out a published adventure - mines of Phandelver has good reviews, and thus should be providing interesting encounters. This group has played through. It was amazingly boring combat wise to play, because none of the combats required me as a druid to mix up my 'go to' combat script. We played pretty intelligently and dodged the two potential fights that could get ridiculous I suspect.
I'm not saying the combats weren't challenging btw. It was often close as to whether someone would die. It was just very straightforward to decide what to do.
Crank up the difficulty by a factor of four or so, to the point where somebody will die unless you change your doctrine and tactics. Enemy hobgoblins entrench every night behind field fortifications (3/4 cover or better), goblins own the night thanks to Nimble Escape and darkvision, drow have designated Faerie Fire spotters, kobolds throw nets and come in large numbers and when things go badly retreat over what turns out to be prepared pit traps, orcs abandon orcish culture as a loser's game and study elvish culture/magic (scro!) and ride horses for mobility and have lots of battlemages, banshees play hit-and-run using their incorporeality to avoid retaliation, dragons leverage their Stealth to get surprise on the party, goblins buy sleep poison from drow, illithids send Intellect Devourers to meet the PCs wearing the bodies of peasants and pilgrims and try to possess PCs when they are asleep, etc., etc. Try to crank up the difficulty in a way that leaves the possibility of counterplay on the part of the PCs, instead of silly fiat stuff like "this dragon has AC 29 and is immune to all magic and poisons."
5E is easy by default. Make it more interesting.