With a light enough load, you certainly don't need a touring bike. A hiker friend of mine tours on his road bike wearing a small backpack. Not for me, but he makes it work.

My first 2000+ mile tour was on a road bike with a traditional heavy load in five packs. It was stiff and uncomfortable but I made it.

My last XC tour (4500 miles) I got smarter and lightened the load to less than 15 pounds base weight in two rear panniers only (this was after hiking the Triple Crown). I had an old steel touring bike with a granny gear, but virtually never used the granny. I learned that with that small a load, I no longer needed a heavy touring bike, so I sold it. (I replaced with a sort of compromise, a gravel bike with rear rack attachments (and disk brakes, which I love).)