I see the debate on guidance continues. It seems to me that the devs may be trying their hand at making many of these cantrips mechanically similar, so it is the same basic design for all of these cantrips. We'll have to wait and see True Strike and Blade Ward to see if I'm right.
I don't think the change to Spiritual Weapon makes it a bad spell, per se, but it will certainly be used less. I'm also not sure I buy that Spiritual Weapon is that iconic, unless by that it is meant that it has been in the cleric repertoire since at least the AD&D/BCMI days. I don't remember it being that much of a "go to" spell for clerics in previous editions, but in 5e has become much more prominent, mostly due to lacking Concentration.
IMHO, the Banishment change is more egregious. It seems that few creatures are going to fail their Save 10 times in a row to actually be banished to their home plane. Granted, PHB Banishment was probably in need of toning down more so than most of the other spells changed, but I don't think this was the way to do it. They could have reigned it in by making it more niche, such that it only worked on extraplanar creatures to begin with. This would have made it powerful, but a universal go to for most situations with a tough opponent that does not have Legendary Resistances. They have a template: a similar concept is in place with the Good & Evil line of spells.
The irony is that outside of 5e, Banishment was somewhat limited, while spells like Protection from Good & Evil were much more universally applicable in play. Now that is reversed. Why not bring it in line by limiting to the creature types in the Good & Evil spells?