I would doubt you’d hit a progression dead end in that game. you’d have to be god cracked at it and enjoy it enough to play that much and milk what’s already there, and at that point you’d probably want to buy the DLC to extend the variety and experience, because it’s that good to begin with.
I started playing this game before there was DLC. You know what? It was fucking fun.
Doors don’t control my enjoyment. I played it at times without DLC installed. I can handle some inaccessible doors being around without letting it control my enjoyment.