Pretty sure it's Scott Manley that did an episode on the aerospike and just how hard they are to get to work right.
Needless to say, getting anything to go to space is hard.
Aerospikes are hard because you cant control the external pressure. At altitude A you have X atmospheric pressure, but at altitude B, Y pressure, that pressure is what keeps the exhaust against the surfave and exerting force, you can only design an aerospike for a certain effecient operational altitude and outside of that its just not great.
A nozzle engine doesnt have to account for this as much because the nozzle is keeping the pressure of the exhaust
Why aren't the dots with the red arrows also planets?
(My brain whenever I see images like that)
I couldnt even see the images there, it was literally a whole page of ads