There is an old Roman proverb that was said when Greeks were making fun of the length of their swords. Romans replied it only needed to be long enough to reach your heart.

Note that the claim that Roman formations are too tight to use spears/axes/longer weapons/etc is a myth. A typical or common Roman infantry formation during the Republic or early Empire is described as having around 3 feet of space between each man. This is a rather spacious formation that gives each soldier plenty of room to deploy spear or sword, and is a more spacious formation than the classical Greek phalanxes that used heavy thrusting spears.

3 feet of space is also comparable to or greater than the spacing used by many pike formations, as many Rennisance European pikemen also had around 3 feet of space between each man and sometimes had as little as only 1.5 feet of space. Even the more loose formation of Ming Dynasty pikemen was still only 3.5 feet between each man according to the Ming military blog.

Thus, contrary to some belief that Roman combat was too cramped for spears, there would be no issue in using a long heavy thrusting spear or a 7 foot pila/throwing spear in melee combat when there was 3 feet of space between each man.

Of course, there could have been and probably were cases when the Romans switched to a much tighter formation where a shorter sword was more manuverable and easier to use than a long thrusting spears or pila in melee.