There are indeed many gods. A god, of course, is anything that is worshiped. Therefore, Hashem is not G-d to those who do not worship him. So, if I say I worship Hashem, how can it be determined that this is true?
Hashem is G-d. We are not. Therefore, the only way we can have a relationship with him is by Him giving us commandments and by us following them. There is nothing else we can do to worship our G-d. We cannot give Him anything he does not already have because everything is His. We cannot really have a conversation with him because a conversation is an exchange of ideas. He can give us ideas, but we cannot give Him ideas. He can give us wisdom and knowledge but, we cannot give Him wisdom and knowledge. We cannot embrace Him, nor kiss Him, nor see Him, nor hear Him. Therefore, since He is so vast, extending beyond limit from eternity to eternity; since he is so lofty and grand and we are so meager, there is nothing that we can really do to worship Hashem as G-d unless He establishes a way.
Yes, we are made in the image of G-d but, in our current state, our attributes are far from being divine. Therefore, this covenant that G-d has instituted is the only common ground we have with Him. It is very extensive, thorough and meticulous. There is a mitzvah for everything and there is a blessing for everything. It extends to every aspect of life so that we have the opportunity to be obedient in everything we do, not ever forgetting about G-d. If we transgress a mitzvah, we know we transgress and we still remember G-d. Of course, it is different if the transgression is deliberate, but in inadvertent transgression, the mitzvah still serves its purpose.
It's not about cleanliness, sanitation or health. It isn't even really about morality or justice. Though there are certain mitzvahs that address these things, it isn't really about any of these things. It's just what G-d said to do and we do what He says to do because He is our G-d and we are His people. Each mitzvah is a memorial of G-d and what He has done and is doing and will do for us. He brought us out of Egypt for this purpose so that we can be a holy people, distinct and set apart--peculiarly His own people. We meticulously examine the Law so that we can meticulously examine ourselves hence knowing where we stand in His presence and G-d does not withhold His mercy from any humbled and contrite heart
People believe what they want to believe. People who believe in G-d do so because they want to and people who are atheist don’t believe in G-d simply because they don’t want to. Judaism, initially, is not about following a bunch of commandments. Judaism, initially, is about the belief in G-d but, believing in G-d is about following a bunch of commandments. The covenant is meant to bring us joy. If one doesn’t enjoy being in the covenant, if it doesn’t make him happy, what good is it to him? It should, however, be the joy of every Jew and others can find joy in it if they see your joy. If you observe the mitzvot, and you enjoy them, naturally you would want others to join you in your celebration. That is what true observance and worship is and celebrating G-d, life and this covenant is how we do that.