It didn't fail, a part did what it was supposed to. It is unreasonable to expect every landing will be perfect, it is reasonable to expect that shock absorbent will be used.

This is just wrong. It failed. It came down harder than intended.

SpaceX had mitigation in place to prevent this from being a complete failure, but this was not intended to happen. This is no different from an engine exploding on the way up. When that happen(ed) it is a partial failure. The fact that they have kevlar blankets in place so that this doesn't explode the entire rocket, and allows the mission to be completed, doesn't change that fact.

If it were never going to be used then it would make more sense to not have it to avoid the expense and the weight.

Just because something can happen does not mean it is a failure. Just because something is a failure doesn't mean it never happens. Mass and weight mitigating the affect of failures is often worth it, e.g. the kevlar blankets mentioned above.

That isn't a solution, the majority of launches won't have the performance to return to land.

Citation?

Even if you can supply me with one (I'm not sure if this is true today), it will presumably not be true by the time SpaceX is launching falcon 9's at a rate that the time back from sea matters. The only way the satellite market's size is increasing that much is if the cost, (and as a result, presumably weight) of satellites comes down significantly.

<The rest of your post>

Really, I think you overestimate the effect of a few days. 4 days return time at most increases the number of cores they need by 3 (assuming daily or less launches).