I think speed being brought up to par a little bit would be a good thing, considering stats are often little more than a trap in a game that usually bends over backwards in its design to make things approachable for new players.

Another reason speed stats suck is most of the jobs in game have an 'Ability' that deals damage, i.e. an oGCD action that does not receive any benefit from speed whatsoever. This of course aligns with their current design centering on predictable damage windows every 2 minutes; ability recasts being reduced by speed stats would cause them to become desynchronized from these windows and potentially make them less powerful if not used properly (see how PLD's EW version of Goring Blade or current GNB's Double Down work). And it's often at odds with the way bosses will leave the field for long periods in many higher end raid encounters, especially Ultimates. There's scarcely any opportunity to even eke out more than 1 extra GCD within the times you may actually attack the boss, let alone a recent boss design more comfortable with challenging players to maintain uptime instead of almost guaranteeing it.

BLM remains notable for being the only job that does not have damaging oGCDs, and likewise has much more often had periods where spellspeed was preferable or at the very least not detrimental compared to other stats.

Putting aside how a faster GCD makes oGCD weaving more difficult, speed's effect on the GCD could be greater. It was already changed to make DoTs tic harder, but so many of those were removed I wouldn't be surprised if speed is weaker than intended currently.