Classic is not the opposite of modern, and in Egyptian homes the two are rarely separated. The most common request in this market is for both at once, which is a real style rather than a compromise.
What carries over
Symmetry, a sense of weight, and detail that rewards attention. A classic piece is usually willing to be looked at for longer. Where a modern object states one idea cleanly, a classic one holds a few, and the arrangement of them is the point.
Mixing without muddling
The reliable approach is to let one language lead and the other punctuate. A restrained room with one ornate piece reads as considered. An even split reads as indecision. If you have a classic dining setting, a single clean-lined piece on the sideboard will sharpen it rather than fight it.
Where it belongs
Dining rooms take classic better than any other space, because the room is already about ceremony and sitting still. Living rooms take it in smaller doses. Kitchens almost never.
Avoiding the pastiche
The failure mode is theming, where every object agrees with every other and the room stops feeling lived in. One genuinely good piece with presence will do more than a set that matches.
What we keep here has proportion and finish worth the second look, without asking the whole room to play along.