This represents a fundamental flaw in Elite's game design, IMO.
Ships are gated by rank, but there is no skill required to attain those ranks, only repetition over a timespan. Just like with the Pilot Federation ranks up to Elite, Naval ranks don't require any special skills or knowledge for players to attain. There are no tests to pass. No achievements to attain. Just do the same things over and over until you make a certain counter reach a certain value. Some people will piddle their way up the ladder, incrementing that counter here and there without paying much attention to it, until they look at their stats and notice "oh hey, I finally made Rank and can get that ship. Yay!"
Others will set that ship as their goal and use every method possible to increment that counter as fast as possible, taking any shortcut they can.
But in either case, it's all about making a number. Or two numbers, actually: one in rank, the other in credit.
I agree with those that say the big ships should be the hallmark of an experienced player, but Elite's design doesn't allow for it. Elite ranking, both Pilot and Naval, should have been constructed from the start to require actual skill and experience, but they don't. You don't have to engage in brilliant trade strategy to become an Elite Trader. You don't have to become an ace fighter to become Elite in Combat. You don't have to discover anything new or venture to distant galaxies or even leave the bubble to become an Elite Explorer.
And you don't have to do anything except haul performance enhancers or donate lots of credits to become a King or Vice Admiral or whatever they are and "earn" the right to buy a big ship, befitting the responsibility, knowledge or skill of someone "entitled" to those ships. Whether or not you see it as a grind or choose to make it a grind it doesn't matter. How fast you do it doesn't matter.
It's just about making counters go up. It will never be more or less interesting than that unless FDev decides to change it.