Yeah I get you 100% and having played the 4E Warlord for 30 levels I just am let down by this take on one of the best things that wonderful edition had going for it. The are some bright points that some people have pointed out like Mark Foe and Rallying Surge. I really like those abilities. Warlords can shout you back to consciousness you have to have it.I think this is a common debate point. At what point is an archetype worthy of its own class structure, versus just being an add on to an existing class? There is no single answer.
I think the Paladin is the OG marshall....the high charisma leader that heals and inspires his fellows. That "niche" was already covered, but just as people enjoy spell-less rangers, people like to have that leader type without holy or magical baggage.
Could the fighter have taken on this role?.... honestly, yes I agree they could. Give them a Marshall subclass to handle some of the bigger stuff, and I think the rest of the class could absolutely cover it. Frankly I also think the flavor of that makes more sense than the Marshall class. Having a "general" at 1st level doesn't really make sense....leadership is not something you just have its something you grow into. Having it be a fighter subclass better mirrors the "got some military experience and then took on a leader role".
Should that have been the case? I think tradition is why it didn't happen. A lot of people enjoy the 4e Warlord concept. Just as the ranger and paladin before them....you could do those classes as fighters....but tradition gave those ideas their own class, and once done, its hard to go back. So I think the momentum of the people's desire is what crystallized the Marshall class.
I think if you could give out all of your attacks and Commanding Presence had a line saying "an ally can make this attack or cast a cantrip no action required and can only be targeted by any Commanding Presence once per round" I would love it so much more.
You can go full lazylord and it doesn't have the potential to be a burden. You are cutting off Shield, Counterspell, Uncanny Dodge and countless Reaction speed manuvers to do one of your iconic components of the character. You can use it to go full Lazylord if you want or you can charge in with your own sword or whatever.
Now I just need to do some reworking on Sanguine Knot and the subclasses.