You are slowing down the attacks. Especially in a game where people barely get too level 12.
No you are speeding it up.
A Monk with a F/R dip or a F/R with a Monk dip gets MORE attacks at EVERY level except 5 and they have the same number at level 5.
A Paladin-Warlock or Fighter-Warlock gets the same number of attacks at every level except 5.
In a game that goes to 10 level 5 is the only level you are getting less attacks
And that's the thing If you're playing in a high optimization game what you're trying to abuse multclassing, The single class characters are hitting their tiered powers faster than you and have more resources to boost their power.
Multicasting with a primary weapon user before level 6 is a trap unless you're using some specialized cheese build.
Explain to me how it is a trap at level 2, 3 or 4 with the new rules.
Extra attack is too powerful to delay because that time around level 5 is when DMs can go pull out monsters that also have similarly strong Tier 2 abilities.
Extra attack does not exist for 2nd, 3rd or 4th level Characters.
Further more with Nick any Monk, Ranger or Fighter who uses lihgt weapons can get that boost in power at level 2 now.
It is only an issue AT level 5. Not before, not after.
Finally this is an arguement for a Warlock dip with Fighter or Paladin, but even here the True Strike cantrip mitigates this. It allows an extra 1d6, so even at level 5 this is not as big a deal as it would be.
A dual-wheeler can do wield and eventually get dual there and get what they would have got with the monk dip without slowing their class progression
With nick you can both dual wield and make a 2nd attack using your action and make a 3rd attack using martial arts.
This is why multiclassing is so much more powerful, Two Weapon fighting no longer competes with martial arts. With nick they both give you an extra attack.
A single class fighter or single class Monk will not catch up eventually, they will be behind at every level.
You get a powerful level 2 but you eventually get surpassed by the single class until the singer class plateaus which is usually in the teens.
When do you get passed by a single classed fighter? You are way better at level 2-4, substantially better at level 6-10 and with the increased martial arts damage pretty darn close at level 5 even without extra attack.