A solid core is a shorted turn (due to induced eddy currents) but, because the core is made of iron, this shorted turn isn't a massively great super-conductor hence core losses appear resistive (as implied by the name "losses").
To minimize eddy currents, laminations are used that are insulated from each other - now there is no longer a shorted turn and the cross sectional area of each laminate is tiny compared to the whole core cross section.
If the core was made from ferrite (a really poor conductor due to how the material is granulated and held together in a type of epoxy resin), the cross sectional area would never be regarded as "too big" because, if you analyzed it as separate isolated tiny pieces of ferrite, the eddy current losses would be minute except as frequency gets really high.
Same mechanism - laminations are OK for AC power frequencies and do exactly the same job as the insulated granules of ferrite material at much higher frequencies. Ideally, a core would have great magnetic permeability and zero conductivity.
Visually, the cross sectional area looks the same of course but not in terms of eddy currents.