While I'm rewatching Clone Wars, there have been multiple times that one of the bad guys slowly parks a ship on a landing platform before starting trouble. I'm not talking about giant armadas - this is often a single ship (for example, Dooku landing on one of the Pike planets in s06e10).
Are there no planetary defense systems, shields, or even security ships? No early warning or radar? Some planets are pretty backwater like Florrum but this even happens on fairly advanced planets. I'd also imagine that some things like radar are relatively cheap in comparison to the cost of building structures, buying ships, etc. to settle on a planet.