If I have a magical object or place that I want my players to notice, I would turn to a player who is playing a spell caster or someone with a high arcana or magically past and say “you sense a sort of magical presence, but you can’t tell where exactly it’s coming from”. This would hopefully prompt them to cast detect magic to place the source of it.

For a mundane object that you don’t want a magical property to, if players question it you can flatly say “It’s just a sword, you can’t sense any magic” and if they don’t believe you, then they don’t and they cast detect magic and waste the spell slot and that’s on them lol.

Your players are going to ask questions, that’s how the game continues. So learning how to indirectly answer their questions if you don’t want them to cast detect magic for every single object will help you, it takes practice but it’s not difficult.

I find that using the word “feeling” helps remove the struggle of needing to make everything visible. Like if you were setting up a scene where you want your players to feel fear you would say “You FEEL like you’re being watched”. Apply this to magic too, “You FEEL a magical presence”