Sarcasm aside, why is melee always so weak?

At least let's say "in the past 5 leagues, the VAST majority of melee skills are extremely weak for most players in most situations.

Yeah, the best players with the most currency and experience can make some melee skills great, yea boneshatter is strong, MS isn't so bad, and flicker (if you consider it melee) can be OPAF with investment, but I still think it's fair to say that :

All else being equal, melee skills are MUCH weaker than spells, totems, mines, traps, or minions.

I'm curious as to why people think this is, not just moaning and complaining, but obviously it's something a ton of people feel strongly about, GGG knows well that this is the case, but it never seems to change. Many times more so if you said physical melee skills specifically.

It would be one thing to say "melee skills require more expensive weapons to compete" but I think it's far more than that...

Playing SSF boneshatter this league and it seems ok.

I've never done the really end-endgame stuff, but my most successful builds were melee.
Bleed Earthquake, Glacial Hammer, Bleed Cyclone, Vigilant Strike (yes, indeed).
One exception being an Ice Trapper, who was by far the easiest to get things done.

So, first sorta rejecting the assertation that melee is currently weak, there's plenty of vectors for melee to be strong, even ignoring boneshatter. (Note strong means it can complete content, not that it's the top DPS).

Now lets set aside damage for a moment entirely as it's a factor outside of PoE, so for the sake of the below, assume that all skills currently deal the same amount of damage to a target over 10 seconds (regardless of the fact that some skills just have better damage than othrs).

So Melee (in nearly every system) has a few issues, the first of which is that it's melee. That is to say, Ranged tools have a dramatically greater opporuntiy for application than Melee possibly can, this is an inheret disparity between the two (and a big reason why real ranged weapons out paced melee weapons in basically every vector that could be logistically supported in their eras). This comes to the front of the issue when it comes to PoE, because so many people favor the choice which allows them to clear maps the fastest, putting added value on these added opporunities to apply attacks (and thus push damage). If a boss has a dodge or die, a melee must run several meters out, then several meters in before they can start applying damage (often waiting up to a second between trips), while ranged can sidestep and instantly start shooting again (or something like Cold DoT, which never needed to stop DPS to move). You see this in MMO's a lot with high mobility fights, though it varies there, if melee can move and attack vs ranged casters who often are not allowed to move and attack (and often must be able to stand still for several seconds to perform one attack).

This comes to PoE's open skill system, allowing players to allocate their own balance of offense vs defense. Because melee MUST expose themselves to harm in a more direct way, they also must invest more into their defense in some way, be it itemizing gear better for defense, more skill points into defense, or heavily dedicated defensive asciendancy. Ranged, by the nature of being able to simply stay away from harm and manually avoid attacks (included things like arrows, fireballs, aoes, etc), plus the use of Dash skills to further enhance this intangable layer of defense, can then invest that into their offensive power. To balance this natural disparity, the base value for ALL ranged abilities would have to be dramatically cut (as much as 30% I'd guess, compared to base values for Melee, if not far more, but have no data, just making up numbers here).

Following this is area, melee tends towards smaller, confined areas, in many systems as few as a single target. While ranged attacks nearly always have some way to hit more than one target, weather it's an inherent AoE like Fireball, chain shots like Arc, piercing like Soulrend, built into the attack, and the supports that add them that simply don't work for Melee due to their implicit differences. While they've addressed this to a degree (strike range, more AoE skills, etc), you simply can't out do that implicit difference, just shorten the gap.

Lastly is an inherent difference in where the start of the math is for the two versions. Most ranged tools are built off their own internal base values, while melee is built off both the base skill and the quality of damage of their weapon(s). Obviously there some middleground here with bows, but a lot of the bow skills favor their own values over a weapon (Toxic rain elemental hit, etc) and care less about the weapon (though no POE bow build cares zero about its weapon). While casters do get a bonus for their weapon (skill levels, bonus spell damage, etc) its a lot less impactful than just skill level compared to a modest gains in base weapon damage is for a melee character. This has sorta been an old as time problem for a lot of systems, a wizard in D&D is just as damaging with a staff as without, generally speaking, while a fighter or rogue goes from modest damage to zero without a weapon, and the difference in their weapon quality reverberates heavily. WoW's melee characters started raids fairly weak, but as they get a raid tier weapon, they shoot way up in the rankings (typically, of course, a lot of work has gone to change this problem in the MMO space)

Well there's a few paragraphs of core disparity between the two that develops into this being either a perception caused by opinion of the value of the opporunity cost of Melee, or the inherent problems in a Melee vs Ranged system that cause a lot of pain points. For my money, I think PoE's got a pretty good balance between the two, but nothings perfect and actual balance is a unicorn to be forever chased, as once captured, it dies.

Because people compare it only to the best of best. ALso it requires diffrent playstyle than anything else in the game.
Melee is fine. Its skill issue.