"Base After Base" is likely the most forgettable main level within Geometry Dash. Of the original 7 main levels in Geometry Dash (which consist of "Stereo Madness" through to "Jumper"), "Base After Base" is the only one that doesn't really add anything substantially new or interesting.

"Stereo Madness" is very memorable because it's the first level you likely played when you first opened the game. Everybody has to start from somewhere… It features two squashed triple spikes which love to catch new players off guard as well as its final coin which was famously nerfed. "Back on Track" introduces jump pads and more infamously is known for the ‘Back on Track is the hardest level’ joke (I doubt this joke is as prevalent nowadays, but it was definitely common when I started playing in 2017/2018). "Polargeist" introduces jump orbs. "Dry Out" introduces the upside-down gameplay for the first time. "Can't Let Go" is known for its timings (which can be pretty annoying for new players). "Jumper" is memorable for its pillar-based structuring (and I guess that one ship section towards the end of the level). I can't think of anything necessarily unique or distinct about "Base After Base".

The upside-down gamemode was already perfectly introduced with "Dry Out", and there's no iconic, striking parts within "Base After Base", such as the ship section of "Back on Track", the memorable overall structuring and gameplay of "Jumper" or the dark section of "Can't Let Go". It's a filler level which I find pretty unremarkable, it only exists to fill an empty space between "Dry Out" and "Can't Let Go"; it could be easily be replaced and there wouldn't be much of a difference. The fact that it's a remnant of the unused beta level "Ultimate Destruction" also doesn’t help, especially as "Ultimate Destruction" just leaves a much stronger impression compared to "Base After Base", partially because of its song. I'm sorry to say, but "Base After Base" is probably DJVI's weakest contribution to the Geometry Dash soundtrack. "Ultimate Destruction" would have been a great song and it's a shame RobTop was never able to acquire the rights to use it.

"Base After Base" isn't necessarily a terrible level, it's just extremely forgettable with nothing particularly unique or new to add to the table like practically every other main level.