Simplistic answer: Why am I playing an EK at all, when I could be playing a Battle Master with Sharpshooter and Crossbow Expert?
Slightly more complex answer: I think everyone has a certain level of optimization, and certain types of optimization, that they're not comfortable letting go of. You can see in the "racial bonuses" discussions that not everyone is comfortable leaving stat bonuses on the table simply to play a different race. You can see that in some early 5e discussions around using a greatsword versus a greataxe, and the minor damage discrepancy between 2 otherwise identical weapons.
Your optimization hangup, here, seems to be that it bothers you to play a particular subclass in a non-optimal manner. I sympathize; but I think hexblade is hardly alone in that concern. Ranged attacks' overall superiority to melee has been a major optimization theme/pain point since 5e's release.
I also think you're still laboring under the idea that hexblade somehow has some sort of at-will damage lag compared to other melee classes, I simply think that isn't true. 2 invocations (thirsting blade and lifedrinker) keep hexblade on-par with all non-fighter melee well into Tier 3, and none of those classes can both boost their attacks AND their spell/save DCs with the same ASIs, so any minor divergence between hexblade and the other classes is more than justified.
I think your right but your responding to the wrong issue. I think the complaint about Pact of the blade warlocks is actually largely about the comparison to other warlock pacts and why they choose warlock to begin with. The comparison of pact of the blades to other fighter builds is not about them falling short of other melee fighters so much as their agility to do that and maintain the reasons players chose warlock to begin with.
Warlock Pact vs Warlock Pact, Pact of the Blade is the only warlock pact that becomes the core of your build and requires your invocations to maintain it. This is dramatically less flexible than other pacts one because its font heavy with Thristy Blade, improved pact weapon, and likely eldritch armor when it comes out taking all of your invocations to level 6. Some might take Eldritch smite instead of Eldritch Armor... I wouldn't I consider Eldritch smite a resource trap twice over, but some might. Your likely taking Life drinker at level 12 if you make it that far. Most people are not likely to hit 12 or go much further so many people are investing 3/3, 3-4/5, or 4-5/6 invocations into pact pact of the blade. With the other pacts you might be using 1... ever. The invocations absolutely make Pact of the Blade capable enough in melee to work. If however, your used to have 5-6 toys by level 12 but now your there with 1 toy your likely not getting the warlock feel your used to. The only reason this is a Hexblade thread is that many people envision the hexblade fixing this by adding damage and defense.
Pact of the Blade Warlock vs Other melee. When you used pact of the blade and all its invocations which until Eldritch Armor is officially released are all damage scaling, you keep up with damage. That's not a problem. However unless your using the Armor of Shadows invocation or playing a hexblade warlock lock your AC defense is lower and your not getting shields, stealth or any of the defensive abilities that other fighters get. You can with a dex build and back ground use stealth, but you don't have rogues disengage or hide as a bonus action mechanic. You don't have the HP or half damage of other fighters. Being happy with even or lower damage is fine, but dying is not fun so a minimum survivability is expected. Using Armor of Shadows is another invocation fix and leaves you in the same spot as Eldritch Armor. Hexblade allows for a more functional dex build than Armor of Shadows because of a lesser investment in dex by using shields which is good because you want good constitution and charisma and don't have any ASI to spare. Hexblade also presents you some defensive spells so when you take the Hexblade
Warlock with a name that has blade in it many immediately think Pact of the Blade but as stated lack the flexibility of warlock and tied to dexterity they are afraid of dying without it but as a warlock subclass expect magic to help that.
Warlock defense vs other caster class defense. So you invested all your invocations you normally play with, your invested into constitution because your afraid of losing one of your two spell slots, you invested into charisma because you don't want to waste one of your two spell slots on a failure if you can help it and your a warlock after all. You invested in the hexblade subclass and dex for better defense. Your holding your own in damage but your still fearing death, because while your AC is about the same your HP is bit lower and you don't have evasion or any other trick to save you. You gave that up when you took Hexblade. But your a spell casters and your spells are going to save you! ... your two spells... at level 6 when most warlocks have 2 spell slots paladins have 6 and Eldritch Knights have 3 plus one more feat than you, "other" full casters have 10. So its good that you have concentration spells so you can stretch out those spell slots... unless you hit because then you could lose it so its good its for defense and you have the second for a back up... but wait... your a warlock! A Full caster! surely you have some magical toys to play with thats why you took warlock! ... well no. You don't. Your one spell is keeping you alive your second is backing that up incase it fails because being with out that defense would be bad. Your ASI are spent on Charisma because your using that to attack and cast spell... so what do you get as a full caster warlock going pact of the blade? Likely 1 invocation. Maybe two. Choose wisely, because chances are every other pact of the blade warlock looks just like you! That's not going to keep everyone from saying your fine with toys and defense because your a full caster! when the reality is your likely casting one spell most fights recasting it if it fails instead of the 1-10 every other full caster uses.
The truth is most pact of the blades warlocks will end up dropping dumping Charisma because they never cast spell one enemies but on themselves for survival. They will push dex and constitution for AC and HP. Then they will cast the same defensive spell once or twice every battle. This is not the gish they expected to play. They expected more magic form a full caster. They expected more toys from a warlock. They expected more ways to play and not fear death than one. ... Pact of the Blade... was a trap. Hexblades allow charisma for several features including the use of the weapon for attack, which reduces the need for high dex but does not remove the need for dex or constitution actually making the build harder on resources forcing a M.A.D. (multiple attribute depend, being more than 2, Con, Dex, & Cha) build with its feature. ...This often means Hexblade Pact of the Blade is more of a trap than other pact of the blades. This is not true for everyone. I know. It depends on your table. A care bear table never has to worry about dying. A story board table may have a full party of charismatic and insightful characters that never seem to fight because they talk their way out of everything. ... but for a lot of tables this is true. The Eldritch Armor invocation can lossen the load on Hexblade Pact of the blades by allowing ring mail or heavy mithril armor variant that allow focus on the two stats of Charisma and Constitution. If they had something to reduce the fear of insufficient defense caused by the loss of the range and the lack of supplemented defense that all other medium armor melee fighters get in the form of greater spell flexiblity or features like the rogues cunning action and evasion Hex blades Pact of the blades would feel more free to cast spells on enemies since they have higher charisma and would feel save enough to do it. A better level 6 defense ability would go along way to that. Additionally if there invocations were not so heavily realized on to bring pact of the blade to where it does poeple would feel more like they were playing a warlock.
Three things that would dramatically change how players feel when they play a Hexblade pact of the blade:
1. Remove the Thirsty Blade invocation tax by taking Booming blade and green flame-blade and use them every time to free up and invocation and feel a bit more like a warlock since you get the cantrips and they are using your whole action making them incompatible with Thirsty Blade.
2. Ignore the Eldritch smite invocation and get a +1 magic weapon instead of improved pact weapon.
That gets two maybe 3 invocations back.
3. Consider the idea of using heavy armor to play with low dex focusing on Constriction and Charisma, then use ring mail and mithril armor to reduce the M.A.D. requirement while Eldritch Armor would be on way to this and Heavily Armored feat another, I would suggest asking your GM to let you use Training Down Time in Xanthar's Guide Everything to Learn Proficiency in heavy armor. It normally only does tools and Languages but it would be reasonable to use it to pick up a weapon or then next level of armor prophecy with a character's access to a teacher, time, and gold. I would personally just give them the heavily armored feat on completion of the training. This might make things hard for the first few levels until you get it or you might convince a GM to take let you take a commutative and permanent -2 from from your stats at level one to start with the feat, or perhaps more simply take human variant to pick it up from the start.
