Is a firm landing an indication of the pilot inexperience?
First of all, the landing should be in the touchdown zone. Often I see pilots try to achieve a very smooth landing but floating far out of the touchdown zone before touching terra firma. Then they have to brake hard and taxi of at the far end. There are no points for landing outside the touchdown zone, even if it is the smoothest landing imaginable. In many overruns, landing late is a contributing factor.

A good landing is in the touchdown zone, firm enough to quickly spin up the wheels (and prevent wear by smearing rubber over hundreds of feet), and not so hard that it bounces up again. In calm winds, that can be very smooth, cross wind and wet / contaminated runways require a bit more of firm landing. 

Hard landings1 can occur due to turbulence (wind shifts), upslope of the runway or when the air density above the runway is lower due to heating (typically in calm winds, with sun heating the runway surface)  

So a hard landing is not necessarily an indication of pilot inexperience. However, some of the hardest landing I have ever experienced were when I joined in a training flight where new airline pilots were practicing landings in a Boeing 737 for the first time after their simulator training. I wouldn't be surprised if the runway was dented :-)



1Hard landing is used as a colloquial term here, not in the context of EASA CS 25 §473. See this answer for that context.