No, if everything else within your sentence makes sense then we will be able to understand what you're trying to say. However, it doesn't sound nice if you use wrong articles in German, so you should try to learn the right ones.

German is a language that must be spoken rather correctly or it's hard to understand. This said, the correct use of der, die, das is NOT that important and you will be fully understood if you get it wrong.

Yes, you cannot avoid them! Try and learn each noun with its article - unlike English where there are no genders, German nouns are either masculine, feminine or neuter with a different article for each. The form of the article also change for the case of the noun but once you learn the patterns of declension for each gender, you will be able write each article correctly.