The short answer is yes. Moral theorists intend for their ethical theories to be objective; in the sense that you could derive the answer from a series of rules/axioms/principles/etc. An objective morality doesn't require some supreme lawmaker to act as the moral source, and some might argue that it could not be the case that morality originates in this way (i.e. Socrates/Plato's Euthyphro).
To find a moral philosopher that describes an objective morality without appeals to the divine, we need look no further than Kant. He believes that morality ultimately derives from human reason, and requires nothing else to justify.
There are some fundamental issues with the line of reasoning that without God (or some other divine lawmaker), morality serves no purpose. It denies the essential goals of morality, and tries to reduce it to a chess game where moves are only made to advance your position.
Why should I abstain from breaking an ethical code if I am assured that there will be no negative consequences for me in life, and only oblivion awaits me in the afterlife?
In essence you are asking:
What sorts of material benefits can I expect from playing by the rules?
I think that for all of his faults, Kant does an excellent job of deconstructing this sort of ethical question. When discussing what one ought to do, Kant distinguishes between two types of ought-statements: hypothetical imperatives and categorical imperatives.
A hypothetical imperative is an ought-statement that deals with questions of prudence. If you want to do well on your next exam, you ought to study and prepare for the exam. Nobody would think you immoral for not studying, just imprudent. Another way of viewing these statements is that they are logically contingent upon circumstances. I personally believe that religions with a reward are ultimately making these sorts of statements, which I will touch on later on.
Categorical imperatives are logically absolute. They apply in all cases, without regard to circumstances. You ought not murder, is a categorical imperative in Kant's eyes, for reasons which are beyond the scope of this question.
By asking why you should obey a moral code if it doesn't promise a reward, you are totally missing the point of an objective morality. You are trying to treat categorical imperatives like they are hypothetical imperatives; i.e. not like a moral code. Even when we don't argue from the position of Kant's strict deontological ethics, I think we find similar issues. Utilitarians are concerned with human welfare (in one form or another), and virtue ethicists are concerned with cultivating positive qualities in people; neither of which promise an everlasting reward. Ethical theories that are concerned with reward and the self are generally labeled egoistic.
So yes, I do think that moral theorists intend for their theories to be objective, and no, I don't think they intend for their theories to be treated like religion. Moral theories grounded in reason and human welfare are more sophisticated than "If you do X, I will give you Y," which is what most religions essentially state.