If you ask me, modern authors have a habit of putting too little into a book! But of course your criticism has merit. Les Miserables is indeed very long, though I don't think any of it is waste.
19th century long form fiction is TV show for the time. Weekly episodes in mainstream newspapers. Hugo, Flaubert, Dumas, Zola used the format for decades. People will find Game of Thrones "too little into a show" soon enough, too.
10 episodes per season is indeed too little for a show. Especially when you have like 20 main characters.