I’d suggest a few things that could help considerably.
1 Make two levels of DC - one just to draw boxes, the other to draw detailed racks. Do all your top level planning layout using only the simple box DCs.
Then at the end, select only the simple ones that you need to see close up in any renders that you make, and use Component Browser to Replace Selected. The latter will still take ages to render, though, if you replace too many of rhe simple boxes, as you could easily create millions of edges, especially if you use too much detail in the shelving racks.
2 As well as the DC just to draw boxes, consider adding texture on the box faces to represent the racking. Don’t make it overly high resolution, and just have the texture repeat for each bay of racking, on a single face for the whole aisle.
You could either do this in a low and hi-res version for planning, then rendering (with separate DCs), or even mix and match with the detailed racking modelling depending on how closely you want other people to be able to view what you are drawing.
I’ve just been helping another user on the this forum wrestling with a similar issue of over-detailed imported 3d warehouse models. See this thread for some further suggestions: