Which people where and when?

You don't need a "spice trade" to have spices. People often find sharp-flavoured things that grown in their own neighborhood to eat.

In the Americas, they discovered, ate, domesticated, and bred to new levels the chili pepper. I don't call that bland.

In most of the Old World, they had local garlic, leeks, and onions, also horseradish roots around the eastern Mediterranean from a very early time. Cumin was used in Sumer, and is native from the Mediterranean to south Asia.

In Szechuan, they had their own "peppers" (aka Chinese coriander) from a citrus-related tree. Varieties grow around eastern Asia. It was used in China, Tibet, India, Thailand, and Nepal. There's another close relative in Japan and southern Korea.

Of course, Asia had it easy or easier getting the true peppers of the Spice Islands, but ginger is very widespread in cultivation.

North Africa had the famous silphium of the ancient Mediterranean. Radishes also have bite.

So pretty much, food could be bland if you wanted it that way. But there were plenty of alternatives.