The Republic, though it has its faults, is still better.
"Democracy is the worst form of government, except for all the others".
The Republic is in drastic times and have to, therefore, use drastic measures and can't handle everything. Even more so in the Outlander Saga because the Republic is starved of their resources by the Eternal Empire and can't help. The Empire can because it has less morals and have a more prepared militia, harder soldiers, and a "If you don't do this, you die attitude". I do think that the Republic should be better and Malcom, having been through a lot of ---- and, in the book Annihilation, has been described as a more layered character and not entirely good.
In conclusion: The Republic is broken, but it can be redeemed by those willing to help.
Many people can be influenced by the ideal of peace to make war. In the Prequels, Chancellor Palpatine was influencing Anakin to give up the idea of the Republic and the Jedi for peace, justice and security when Palpatine will only manipulate. The Sith will probably do the same. Lead you astray then back stab you "when something has no more value, discard it.". Acina might not back stab you but someone else can take the Empire and rule. By joining the Sith, you might only damn yourself to a path of darkness