Is there stuff in the storage space that you’ve been cleaning these past few days that belongs to someone else?
You don’t get to decide what to do with things that belong to the living (it saves on future arguments!).
If the person no longer lives at your house, contact them, explain what you’ve been holding onto for them and ask them when they will go through or take these things. If they say they don’t want the stuff, remember, it’s their decision. Set a date in the next few weeks for either donating or tossing their things. (This gives the owner of the items a buffer before they no longer own the items.) Send a text or email outlining what they’ve given you permission to get rid of and by when.
If the owners live in your house, ask them to find things that they can donate to charity or sell. If they insist that they need to keep everything, request that they organize the items, perhaps containing the collection to a corner of the room or space, so you can continue decluttering the area.