You don't need fusion power to melt ice, to move regolith over habitats for shielding, or to melt rocks to extract and process metals. I have absolutely no idea where you get the notion that it meeds fusion power? Solar power or things like kilopower reactors are a great option for Mars, especially for bootstrapping.
Mars is infinitely more viable than anywhere in Venus for the simple fact that you are on solid ground with resources all around you.