What makes dumplings ("knödel") mushy and sticky ("patzig")?
The international dumpling clan is a quite diverse family:  

They come in a lot of sizes, from tiny, bite-sized gnocchi to huge, family-sized serviettenknödel and are made from a wide range of bases, like ricotta, potatoes, stale bread, breadcrumbs...

If you were in an Italian restaurant, you probably were served some member of the gnocchi family - and your description of size and shape supports that. Now gnocchi can be very light and airy, but they quickly turn sticky and mushy, both from overworking the dough and overcooking, from undercooking („raw“ centers), sometimes also because they were prepared in advance an not cooled/stored/reheated in an optimal way. And some types are a per se a bit denser than others.

Without seeing and tasting the food you were served, it’s basically impossible to fully explain what happened and whether they were within the usual acceptable range or not.