The idea is to encourage great people to use their secondary abilities.
For example, great engineers get better yields from each manufactory. So you can expend them right then for getting the wonder of your choice, or you can produce a manufactory so the following engineers are better.
Great writer behaves similarly, you can get culture on the spot or produce great works that will increase your base culture, making next writers better at the cultural bomb.
I am uncertain about what it is exactly current mechanic for great artist, but it seems to depend on your civ base gap rather than the number of great paintings.
The problem with this approach is that it is exponential, so it is easy to have overpowered people in the late game or underpowered people in the early game. What ought to be reduced is the grade of the exponential.
I see a deeper problem than the one you mention here, because the details haven't been hammered out well enough.
Whereas a GE can be used early on for a Manufactory or to Wonderbuild, a GS has no such option - it's a complete waste to bulb a GS early in the game, and is only useful by first building Academies: then the issue is that Academies are the default choice until a certain point in the game, at which point the bonus from Academies is no longer useful, at which point you switch to bulbing. Simple math, and no actual choice involved.
To put that another way - I see this as a deeper and more neglectful version of the other thread where we are talking about lack of choice in policy trees. I think we can set this situation up like this:
GE - Choice is active pretty consistently.
GS - Choice does not exist.
GA - There is some choice, but it depends on the situation. However, I'd say it's pretty bland through and through - you start with GWorks until you can get perma GA, then you do GWorks again.
GW - Pretty much the same as GS imo, there's not much choice here.
GM - This one has some choice later on based situationally on whether the Tourism from the Work is more useful globally than a targeted Tourism on a particular Civ.
GM - Is say little choice here as the duration for WLTKD is so pathetic without having used some towns first to make the choice easy early on before the switch.
GD - Some discussion going on in another thread about changing this.
GP - This has actual choices I'd say, but the real choice is whether to build one at all.
Overall, I would say that about two Great People or maybe three have authentic choices around them that aren't determined by how many Works/tiles you've made.
If you wanted to give the two uses actual choices, you'd plain and simply need to change he effects or mix them up a little (eg Scientists build Manufactures but bulb science; Engineers build Academies but bulb production).
