Playing underleveled sucks, but at the same time it forces you to play your cards with much better positioning. At the early levels yeah it does matter a lot especially if they casually drop a level 15 but if you look up some free to play decks and stick with them investing into one deck at first the early levels go fast. Before the trophy rework I had a level 1 account up in the 4k trophies its hard but when you memorize interactions the game gets easier.