By 1990, the concept of scrolling shooters was well established, and the new Mega Drive had some excellent examples available at (and shortly after) launch. There had been a number of conversions of R-Type to home computers and consoles. People knew how to make shooters exciting.
On first impressions, Planet Smashers is not exciting. A sparse backdrop (a few scrolling stars) is not a promising start, and the graphics are nothing special - even when considering the capabilities of the 7800. Your ship is various shades of grey with a blue cockpit, enemy ships are mainly grey, your status bar is grey. Grey.
It is seemingly impossible to avoid all the bullets coming from the boss, so to get past this stage you will need a lot of luck, a lot of lives, or both. I had both only once, and progressed on to the next part - where you start again, with different warp colours.
It's not a bad game, as such, but sitting here in 2020 there are countless other, better, games you could play instead. Had this come out in 1986, it would be an interesting stage of evolution of the vertical shooter. As it is, it's just a bit dull.