I'm just gonna point out that we don't know what the developers' intentions are. For all we know, summoner is a main class that got implemented not only late in the game's development, but also from the top-down as evidenced by the fact it has its own Celestial Pillar.Here's my issue with you, right. You wanna talk about plain common sense, but are unhappy with the intended progression of Early-Game Summoner Class. Instead of fixing a very easily remedied issue, that I'm certain you know exists, you'd rather ice skate up hill against the vision of the developers?
At least, that's my assumption. The endgame build has a very clear goal, but that's unfortunately post Moon Lord. There's little to no groundwork leading up to it, but plenty of opportunity to make it happen. How you do this is add more content for summoners that can be obtained by crafting rather than dealing with RNG. Pre-hardmode could use a pre Queen Bee armor plus a few craftable staves to smoothly progress from game start to that boss. Hardmode could get a few staves that can be crafted from ores/chlorophyte/shroomite or upgrading existing ones like the Hornet Staff to Moss Hornet Staff.