Technical skill, also referred to as just tech skill, is one's ability to manipulate a controller and produce their desired inputs. Players with greater technical skill are able to more reliably produce their intended inputs, and more efficiently perform maneuvers that require more complicated inputs (such as advanced techniques). Players with lesser technical skill are more prone to input mistakes, and are less able to utilise complicated maneuvers; such players tend to rely on superior cerebral play (such as utilising mindgames) to overcome their technical shortcomings. Technical skill is just one of the many skills required to excel at Smash; technical skill alone will not bring a player much success. However, it is common for inexperienced players to overrate the value of technical skill, and in some extreme cases, see it as the only "true" skill, completely neglecting the importance of other skills despite players often losing to others with less technical skill.
Technical skill in relation to characters
The amount of technical skill necessary to be successful in competitive play is largely dependent on the characters a player uses. Some characters require greater precision, faster fingers, and have a greater reliance on advanced techs, and as such, will demand a greater amount of technical skill to play successfully at a high level of play. In Melee, the prime examples of such characters are Fox and Falco, both of which demand an incredible amount of technical skill to play at even lower levels of competitive play, each relying on incredibly quick movement and heavy utilisation of their Shine combos. In Brawl, the prime examples would be the Ice Climbers, who rely on desynching and chain throws that demand precise timing, and Diddy Kong, who relies on heavy utilisation of his banana combos and locks. In Smash 4, Rosalina uses desynching much like the Ice Climbers in previous games, and Ryu relies on chaining unusual button inputs into intricate combos.
On the other end, some characters also have a lower technical demand, as they rely on more cerebral play with less utilisation of advanced techs and less frequent inputs. In Melee, such examples would be Jigglypuff, who instead has a reliance on aerial pressure and spacing as well as its wall of pain, and Marth, who relies on spacing with his superior reach and utilising his less complicated but deadly combos, such as the infamous Ken combo. In Brawl, Marth is again a prominent example of a character with less technical demands for similar reason as in Melee, and Meta Knight is a particularly noteworthy example as well, as he tends to rely on overwhelming opponents with his incredibly quick and superior moveset, without much utilisation of complicated advanced techs; Meta Knight's particular ease-of-use for a character on the top of the tier list was a frequently cited point for the subsequent banning of the character. In Smash 4, Captain Falcon is an example of a character with low technical demands, as he relies largely on uncomplicated combos (typically initiated from a dash grab) and occasional punishes. Diddy Kong was an example prior to his nerfs in version 1.0.6, as his metagame almost entirely revolved around his various throw combos, which were easy to learn and initiate.
Necessary technical threshold
From the transition of Melee to Brawl, the game's physics engine was made much slower. Characters have universally lower falling speeds; L-cancelling and wavedashing, techniques that sped up characters and gave them more movement options, were removed; and Brawl added the ability to air dodge or use an aerial out of hitstun, lowering the number of true combos that can be performed.
This drastic change in gameplay has since been a heated point of debate in the community. Supporters of Melee generally criticize Brawl for its much more combo-unfriendly physics, claiming that Brawl is too heavily focused around the neutral game, as the defending player frequently has more opportunities to escape being punished for their mistakes than they should have in a fighting game. They also argue that due to the lack of mobility options outside of situational additions such as the DACUS, the game lacks depth in player interactions and is less competitive as a result. Supporters of Brawl criticize Melee for having too high of an entry floor, citing the need for excessive and arguably unnecessary inputs to even stand a chance in competitive play, which reduces its cerebral depth. They also claim that Brawl emphasizes the ability to outread the opponent, which they view as the most important aspect of Smash, and allows slower and less precise players to compete where they otherwise could not in Melee.
However, newer developments in both games have shown that some of the above arguments are not always true. Brawl, while having less advanced techniques, requires much greater precision in input with the ones it does have (such as glide tossing), even moreso than in Melee due to the input buffer. Melee also does require a great amount of cerebral skill to succeed, but focuses more on smaller-scale reads on the opponent's spacing and movement, rather than hard reads on what option they will commit to. Additionally, there exist players in both games who adopt outlier playstyles; for example, Mr. R is a very "flashy" Brawl Marth player, having fantastic movement and pulling off unexpectedly long combos that are seen as uncharacteristic of Brawl. Drephen and Borp, on the other hand, are "slower" Melee Sheik mains, preferring to go for hard reads and tech chases instead of combos, and applying the wavedash and other advanced movement techniques much less often than the average Melee player.
In Smash 4, the ability to airdodge out of hitstun has been significantly weakened, reinstating the importance of combos. Additionally, as of update 1.1.1, shield-stun has been drastically increased, reducing the relative strength of shields and encouraging more offensive gameplay. The increased hitstun, weaker shields, and several other factors Brawl are often cited as the reasons for Smash 4 being faster and more competitively viable than its predecessor. However, it is debatable whether Smash 4 requires more or less technical skill to play than Brawl. While the game reintroduced the ability to pivot, which allows for some more spacing and comboing options, it removed other mobility options such as the DACUS, and previously highly technical characters such as Diddy Kong and Snake were either made much simpler to play or removed from the game.