That's somewhere we differ. I'm of the opinion that it's better to let the players make the build choices for their characters. The DM already controls everything else in the world. The PCs should be the purview of the players.
You've said you play a pretty heavily house ruled game, so I'm not sure whether that's applicable to those who play RAW.
Picking magic items so fighters can fly, etc. as others suggest means those items are part of the game, which the DM (for whatever reason) might not want. Also, the DM can remove any spell from the game for any reason, so even if you play RAW and allow casters to choose spells when they level, the DM really has final say.
Like in life, the players purview is deciding what their characters DO, not what they GET. Some DMs don't play that way, I do.
You've said you play a pretty heavily house ruled game, so I'm not sure whether that's applicable to those who play RAW.
Well, for one thing, our house rules curb the power of casters, especially in tiers 3 and 4, and have (in one fashion or another) for over a year now.
If your split build is RAW, mind sharing how you do both effectively?
Well, you can do a melee / ranged DEX build or a melee / thrown STR build or split the difference.
For example, instead of trying to have a 16 in STR or DEX, I'll have a 14 in both. Sure, my bonus is -1 compared to the optimized build, but they are weaker in the other way by typically being 2 or 3 less, as where I am +1 or +2 better than them.
It is just about balance instead of optimizing IMO. One of my favorite point-buy arrays is 14, 14, 14, 10, 10, 10. Now, even without racial ASIs I can be +2 in three things which are important, but no dump stat penalties. And with the +2 racial ASI, I can still have a 16.
If I do the racial ASIs right, I can even have 14, 14, 14, 14, 10, 10.
Check how the object interaction rules work. It's hard to get that second attack when you can only draw one weapon a turn.
Not if you already have weapons out, like when you are carrying those extra 2-3 spears in your shield/off-hand.
Also, Dual Wielder allows you to draw two weapons. And IIRC WotC has released either feats or fighting styles in later publications which allow you to draw a thrown weapon as part of the attack.