No the parent is correct. Steel is by and large stronger than titanium of the same size. Pray tell what is this "most commonly used alloy of steel"? Because just fyi different steel alloys are used for different applications just like different titanium alloys are also used for different applications.
Titanium has excellent strength to weight properties compared to steel. A 4mm titanium plate would absolutely be dented by common shop hammers. This doesnt mean that "titanium isnt strong" it just means they have different material properties.
Steel has a range of strengths. The "most commonly used steel" is probably just mild steel and yeah Ti-6Al-4V is going to be the rough equal of mild steel on strength broadly assessed. But a high strength steel alloy will be three times that strong, and titanium can only be pushed so far.
For most non-architectural design goals striking the right balance of toughness strength and hardness is generally what you want correct? I would imagine for building a bridge you care much more about elasticity and creep strength.
Bicycle design is a good example of where this matters: steel has a significant fatigue limit, and can endure cyclic stresses below that limit indefinitely. Aluminum has no fatigue limit, so any flexing is inevitably eating away at fatigue life. Thus aluminum bike frames have to be made much stronger and stiffer than otherwise necessary, to avoid bikes breaking unexpectedly due to fatigue. And that in turn means that aluminum bike frames don't have as much of a weight advantage over steel as you'd expect.
