I own a couple of slide projectors, but I'm not a big fan of slide projection. Not only do I believe that projection causes slides to fade if projected too much, but I also think that the quality of the projected image is entirely dependent upon the quality of the projector's lens, which is probably much lower than the IQ of the lens used to take the photograph.
Yes that is quite correct. The lens for projection of slides is not as unimportant as some may think.
But notice : Most slide projectors of modern type ( 1989 - 2003 ...

....modern ? ) had real good standard lenses (Leica pradovit a.s.o.) these companies also offered real excellent lenses in addition (higher priced). And with midt format projection (6x6 for example) there never have been bad lenses.From my point lenses of Rollei (and others) were allmost the best - money can buy - and these projectors were standarisized equiped with.Digital projection is comming better and better.But to the next 5 years it will be much more expansive in comparison. .....(If your digital projection is with 8k you can have better quality than 35mm slide today - but have you ever noticed the prices of such equipment?)With 6x6 or higher it should be the identical quality (compared with 8k).........so "analogue" projection is still "state of the art in 2018"...
with regards
PS : In our company we had different types of video projection walls of some "generations" over the years. They all were highest priced (last I remember came 2009 into scratch - the price some years before was around 30k

)