No one needs a CDN to serve text quickly; that is massive overkill.
CDNs in general are massive overkill for most sites. What a CDN does is reduce latency due to lightspeed. Is lightspeed really why it takes a site 10 seconds to show text? No.
As you point out, caching and proper javascript management is the key to a site that shows text quickly. CDNs do provide caching, but are a complicated and expensive way to do so.
CDNs do a whole lot more than that. They allow common resources to be shared between sites. If 10 sites self-host jQuery, you download it 10 times. If they all pointed to the same CDN, you'd download it once, reducing your latency to below lightspeed - the time it takes to check caches on your device.
This is not a feature unique to a CDN; the same result could be achieved by simply hosting jQuery on a single server and pointing all your websites to that copy.
My point is that when people talk about using "a CDN", usually what they are really talking about is caching. Whether that caching happens at the origin or the edge makes a very very tiny difference (the lightspeed difference).
CDNs in general are massive overkill for most sites. What a CDN does is reduce latency due to lightspeed. Is lightspeed really why it takes a site 10 seconds to show text? No.
As you point out, caching and proper javascript management is the key to a site that shows text quickly. CDNs do provide caching, but are a complicated and expensive way to do so.