I don’t think a particularly strong case can be made for why you run faster while carrying a spear or a broadsword than you do carrying a bow, pistol or SMG.
The devs can de-glitch-ify melee combat, and hopefully they will, but that won’t make melee weapons suddenly become relevant. As long as ranged weapons operate at or near modern weapon levels, regardless of how well the skin looks like a beat-up scavenged homemade contraption, this will be an almost exclusive shooter game. Guns would need to be the equivalent of pipe shotguns, including rifles and pistols, with significant and specialized disadvantages. Modern weapons might drop, but the precision ammo required to use them should be very rare… only brought out for special circumstances (1994’s No Escape).
If we’re looking for a way to blend melee and other lower-rated weaponry in the game at the same time, you have to be looking at the conflict between firearms and tomahawks in the early to mid 18th century America. Otherwise, melee weapons will likely remain merely the weapon of choice for naked newbie beach brawls, discarded or used for wall-bashing after day 3.