When it comes to vintage bicycles, there is no definitive answer. In general, a vintage bicycle is any bike that is at least 20 years old. However, some people consider any bike that is at least 10 years old to be vintage. Ultimately, it is up to the individual to decide what qualifies as a vintage bicycle. There are a few factors that can help you determine if a bike is considered vintage. First, take a look at the frame material. Older bikes were typically made with steel frames, so if you see a steel frame on a bike, it is more likely to be considered vintage. Another factor to consider is the components of the bike. Older bikes often had simple components, so if you see a bike with basic pedals and handlebars, it is probably considered vintage.
Finally, take into account the overall condition of the bike. A well-maintained older bike is more likely to be considered vintage than one that has been neglected over the years. If you're not sure whether or not your bike qualifies as vintage, on the side of caution and assume it does.
Location: Jacksonville, FL, USA
From what I know (which is very little) the condition of the bike has nothing to do with it being "vintage", "classic", or "antique"; it is primarily its age since you can certainly have a beat up "vintage" bike or a nicely maintained bike that is not "vintage". The term vintage specifically referred to what year a wine was produced and that could be from a year ago or before so using it as a generic term for other things makes it become rather vague in its present usage to categorize a bicycle and other stuff. "Vintage" is not definitively defined by how old a bike is so it is up to a buyer to determine the criteria for what they would consider vintage, classic, or antique. As a generality, you can have a vintage carbon, Ti, aluminum, or steel frame; it just depends on when in that technology's evolution the bike you are thinking of purchasing was manufactured since all of those have been around since the mid 1970s or earlier.
If you are trying to ride a classic style bike it would also depend on what type of bike (road, mtb, cruiser, balloon tire, etc.), but it depends on what YOU consider to be "vintage".
I would not consider my carbon frame to be vintage (but some people would) even though it is probably about 20 yrs old, but my 80s/90s steel bike was vintage in my opinion, but not necessarily to others.
I say ride what makes you happy be it looks, performance, or whatever. If it's a bike you like that's what really matters.