I believe some small ships are 100% redundant whether you have easy credits or super hard to get credits meta - some small ships are partially redundant based on play style preference
In my opinion:
1. Sidewinder - 100% redundant beyond insurance last gasp, and starter for new players.
2. Hauler - 75% redundant, everthing afterwards hauls more but does serve specialty role as buy-then-sell Space Taxi and Super Cheap Explorer
3. Adder - 85% redundant, same as Hauler, but only role as Space Taxi
4. Eagle - 100% redundant, is simply there along way to Viper
5. Viper - 75% redundant, on way to Vulture but not 100% out because some players could argue prefer how Viper flies vs Vulture
Not redundant - completely play style preference
Cobra and Asp - players with fully A rated Anacondas can and still do enjoy using these ships for small multi-role purposes, these two are awesome at it
DBS and DBX - better pure combat ships exist (Vulture, Courier) but there are factions of players -including me- that love the niche role these two ships provide. Combat Explorers - I think if and when aliens ever ever the picture where we really need
combat explorers, and not just unarmed explorers, these ships will shine more. But as it, some people still love em regardless what other huge ships they have
Imp Courier - small and relatively cheap but totally non-redundant in my view. Serves as very viable and different role as main combat ship if you don't like the power management of the vulture. Different kind of fun, not better fun than a vulture.
Type 6 and 7 - I think some can argue that both these are redundant progression ships if you're in the trade line but I would say no
a) type 6 is so highly customizable to various roles, including light exploring, mining, etc, that it can and does serve a purpose regardless whether you have made Elite and pimped out your Anaconda
b) Type 7 is an awesome medium trader, anyone that drives the type 9 space cow has to learn to love it or they go crazy. the type 7 is the last large'ish freighter in the game where you can still pretend you are a 'pilot'. If you move to the next progression type 9, you are no doubt about it, a big rig driver

*I owned a type 9 for good chunk of my Elite play experience, which at 3.5 weeks I know isn't much but hey, feels like a ton of hours to me
So there you have it, all the other ships are basically the end of the line for their current progression or big ships that may or may not have a purpose (Fed Dropship?) but cost enough I wouldn't classify them as small ships for redundant yes/no question