Learn English – History of “X is dead. Long live X”

To understand what this simple phrase means first think of the literal meaning, that the person was abandoned because it was assumed that they were already dead, mortally wounded or that it was inevitable that they die.

But there is more to the phrase than that. In common usage, this phrase is often part of a narrative where a person was expected to die, yet against the odds they survived. Some examples from COCA:

Left for dead by a busy road, Susan managed to get a ride to a police station where she insisted she be brought to the Nairobi Women's Hospital.

Pueschel, just 11-years-old, was beaten, stabbed and left for dead, but he lived to testify against Reginald and Gerry Mahaffe.

... a young man in Los Angeles was robbed, shot, left for dead, but he lived because a bullet was stopped by a radio in his pocket.

The common theme in these stories is an act of cruelty towards an innocent person who survives either by a stroke of luck or a miracle. A proper reading of the title Left for Dead should include cruelty, abandonment but also a sense of hope.

It sounds as if you are trying to convey a binary status such as active and inactive. This is one of the many meanings of live

2.: exerting force or containing energy: as
a : afire, glowing live coals
b : connected to electric power
c : charged with explosives and containing shot or a bullet live ammunition;
also : armed but not exploded a live bomb
d : imparting or driven by power a live axle
e : being in operation a live microphone

Each of these uses suggest the ability to turn the status on or off. This is a common usage in American English.

It is true that alive can also convey active status

2 . a : still in existence, force, or operation : active kept hope alive
b : still active in competition with a chance of victory must win to stay alive in the playoffs

However, this usage is not common where there is little direct control over the alive status. One would not say an alive circuit or alive ammunition. In fact, alive is more often used as a predicate adjective than an ordinary modifier.

The passengers were alive!