Retreat? Dont need to retreat if its dead. 5E fighters also make good archers.
A strength-based fighter makes a bad archer. The existence of fighter-archers doesn't change this.
Most dungeons are small as well so range is rarely a problem.
This is a "DM arranges things so your fighter isn't incompetent" solution.
The battlefields I'm used to in most games are often outdoors, usually large, enemies are usually not "will fight to death" but have some goal that the players oppose (which can be "kill the players and loot their corpses"; but they value their lives).
Retreat is common: ambushes, traps, falling back, using summons as disposable threats, etc.
PCs rarely get to pick where they fight. If traveling, it will be an ambush by predator-equivalents (or stumbling on a lair or whatever). If targeted, will often be attacking a modestly fortified position (only if we get very lucky can we get ahead of a foe we want to attack and ambush them while they are traveling).
Mobility is highly valuable, as is range. For an archer-fighter this isn't a problem, but for a strength-fighter it makes things hard as thrown weapons are short range.
Rogues are dex-based, and have bonus action hide and dash; they can range-fight reasponable. Rangers are almost all archers; if melee, they tend to be dex-based so secondary archers. Monks and Barbarians have movement speed buffs. Spellcasters are all ranged. Which leaves Paladins and Fighters; Paladins get a mount at level 5, a movement speed buff.
Strength-Fighters get a 30 foot move speed, a second wind 15 foot dash, can burn a key combat boost (action surge) to run an extra 30 feet. They do get high athletics to jump over terrain? But their mobility sort of sucks, and their ranged attacks have disadvantage beyond like 20 feet.
If they can close with the enemy they can use feats like Sentinel and trips and the like to become a bit sticky; but not super sticky (far less sticky than a 4e fighter).
RAW 5E essentially easy mode much like 4E. 4Es even easier though. Low damage from monsters + healing surge. 5.5 ones hit hard at least.
Games of 4e I actually played usually boosted monster damage significantly; the designers did it, with MM3 and later monsters having twice as much damage at higher levels (going from something like 5+level/2 average DPR to 7+level damage), and DMs who scaled monsters themselves (easiest was replaced monster damage with "highest damage on rolls", adding rolled damage on crits, or just doubling damage dice), or did both (took MM3 and did max damage).
This had a larger impact at tier 3 (level 20+); at level 5 monsters did 8 vs 12 damage (50%), by level 20 it was like 15 vs 27 damage (almost 2x); by the time you reached tier 3 in 4e (which takes 2+ years of regular gaming), hopefully the DM knew what they had to do to scale monsters for the party.
I find 5e works similarly; the DM works out how to scale the foes (at least number, HP, damage) to make a fun fight.
Have you seen a 5.5 fighter in action?
I've played with some 5.5 rules mixed in with 5.0 rules, but not a pure 5.5 table. It was a multiclass fighter (champion)/barbarian at around 10th level.
Maybe there is something secret in the 5.5 fighter that we aren't yet using I'm not seeing.
