Gallery Shmup: Nova Swarm (Steam)
If you include the Galaga family in your shoot-em-ups, you may want to check out the recent indie entry Nova Swarm on Steam. Even if you looked it over at launch, one of the game's features is a dedicated developer who seriously soaks up feedback, and has been relentlessly upgrading the game, despite the $5 pricing. It might be worth another look already, since it's been out almost two months now. https://store.steampowered.com/app/4765070/Nova_Swarm/
There's two core modes, each with its own leaderboard. One for the more pure arcade experience, and the other with a simple pick-from-three upgrades after each boss. Bosses come every few waves and are smaller, simpler affairs. That waves+boss pattern continues until you clear the main game's 50 bosses, and then it loops, probably endlessly. Upgrades are mainly modest stats (so far), which helps offset the enemy scaling difference as the run goes on, so the upgrade mode feels more like a reduced difficulty than a wild combo build type of experience. There are also a variety of short-term powerups that drop in both modes.
Action-wise, you've got your basic moving/shooting plus a slow-movement button and a "phase" button, which offers brief invulnerability on a short cooldown. There are bonuses for grazing (which you can do while phasing), and three chained phases gets you a single special anti-shot bullet that wipes shots and damages enemies in a modest area if it connects. There are a lot of ships to unlock, which vary on a fairly small range of attributes.
Runs start pretty soft and weirdly slow, so players around here probably need to wait a bit for things to pick up, but you'll surely have a good enough idea what it offers given Steam's two hour refund window. The bosses are weird and feel janky, but once you get the hang of their spazzy movement and odd fake-outs, they can seem less bizarre. Watch for the count-downs on the top-center of the boss--those are generally not to be ignored, and a number of attacks do need you to use your phasing in advance. These are obviously entirely different from bullet hell style bosses.
The game also has a rather ridiculous and off-kilter arcade-oriented personality, which I've found surprisingly charming. That kind of thing doesn't normally play well for me, so maybe give it a chance before you turn voices off :)