After 20+ years, your tent fabric has probably deteriorated. If it smells bad, this is definitely true and the tent should be honorably retired. Set the tent up in your back yard and test it with your hose! I do that even with a new tent (not that I've bought any lately) to make sure I've seam sealed it properly. I spent one trip, when it rained every day, holding a towel up to a small gap I left in the seam sealing process, feeing like the Dutch boy and the dike!

And yes, tent technology has vastly improved in the past 20 years! Tents are far lighter and stronger.