You can, and should, alter the terrain to make things easier.

You can dig a safe area under the altars of three of the bosses. (One of the three is less safe, but doable.) You can put a whole base, practically immune to raids, under the Elder's altar if you want to. Flatten the area to make running easier. Build columns to give you something to hide behind. Clear the area of mobs and plant campfires to prevent spawns, and maybe damage the boss. Put your combat engineering mind to work.

Bring a hoe to the swamp to level or raise ground to you don't have to swim all the time.

Bring a pick ax to the mountains to carve trails along steep cliffs.

Dig a steep sided trench around your base to keep out anything that walks, and cover the entire area inside with workbench zones to prevent spawning inside. Earth walls are also indestructible. Islands make good bases too.