"Second and Third Fleets are out of our control. If we could just draw them back from Steele - save their strength for - "
[...]Delenda Est might not have been quite as bad if 1st Fleet had been able to provide back-up - depending on the circumstances might've even been a victory (doubtful but possible).
I think the point of that quote was more "if 2nd and 3rd hadn't tried to bring the fight to the Tevs, tried to outsmart Steele, they wouldn't have lost the Wargods like this for nothing."
The Elders, Byrne and the Beis would rather Netreba and Calder adopted a similar defensive posture to Byrne. Because rushing in into Steele's traps isn't going to buy time for the Project's deployment.
As Grey113 said though, the defensive posture wouldn't have gotten them the Agincourt ... and also if the Elders, Byrne, etc ... want Netreba and Calder to adopt a more defensive posture, they should explain why. Because from the POV of Netreba and Calder the first fleet's position is just as suicidal since Steele would completely control the tempo and timing of the battles. As he showed at Jupiter and the attacks on Earth, he doesn't need traps to ravage the fleets. Therefore, it would be reasonable to explain that there is a plan, but to enact they need to simply delay Steele, they don't need a victory to force loss of political will to prosecute the war in the GTA. My reading, perhaps mistaken, is that Calder and Netreba aren't even aware that there is an end game scenario devised by the Elders much less what it entails.
However, I would argue that even with delay as the main goal, the most effective delay would still be to use part of their fleet offensively while part of it is defensive. The offensive part would keep Steele from completely dominating the tempo, while the defensive part covers the vital assets and is left in reserve. They might not be as offensive as they are/were trying to score a major victory, but having 2nd and 3rd fleet assets engaging Steele (or tying him down but seriously engaging his subordinates) while 1st fleet acts in reserve is a good plan. This is sort of what's happening anyway, but more than that they need these fleets to be coordinated together to have a chance.