Learn English – Antonym of “capital”

"Spartan" is obviously a reference to the city of Sparta; if you want an antonym that keeps the geographical atmosphere, then I think sybaritic is the word you're looking for:

• pertaining to or characteristic of a sybarite; characterized by or loving luxury or sensuous pleasure

• of, relating to, or characteristic of Sybaris or its inhabitants.

Sybaris (Ancient Greek: Σύβαρις; Italian: Sibari) was an important city of Magna Graecia. It was situated on the Gulf of Taranto between two rivers, the Crathis (Crati) and the Sybaris (Coscile).

The city was founded in 720 BC by Achaean and Troezenian settlers. Sybaris amassed great wealth thanks to its fertile land and busy port. Its inhabitants became famous among the Greeks for their hedonism, feasts, and excesses, to the extent that "sybarite" and "sybaritic" have become bywords for opulent luxury and outrageous pleasure-seeking.

<sub>| It's not a shortcut, it's circuitous. → adjective, paraphrase
| It's not a shortcut, it's a diversion. → not a direct path
| It's not a shortcut, it's a long shot. → not a safe bet, two words
| It's not a shortcut, it's a dead link. → bad web bookmark, two words

Hellion's suggestion of detour is an excellent choice as well, although his other suggestion scenic route appears to be the popular choice. I don't think scenic route is a good choice for the sample sentence, it seems overly redundant. But it works great in other contexts, like: I'm enjoying our conversation, so let's take the scenic route.</sub>

I believe in the context of your use case, you can use circuitous, or one of its synonyms (which include indirect, circular, or roundabout), as in:

| It's not a shortcut, it's circuitous.

: not straight, short, and direct
_{Merriam-Webster online}

For a noun word, you can use diversion.

The connotation is not quite opposite of shortcut, but it will imply the path is not direct.

: the act of changing the direction or use of something : the act of diverting something
_{Merriam-Webster online}

When the word shortcut is used to indicate a relatively safe path, as in "a shortcut to success", a word with a nice ring for opposing it would be long shot.

: an attempt or effort that is not likely to be successful
_{Merriam-Webster online}

Finally, in the use of shortcut in the context of a web browser bookmark, the only opposing sense I can think of is a dead link.

A dead link is a link on the world wide web that points to a webpage or server that is permanently unavailable.
_{Urban Dictionary}

Well, I have further reflected upon stale link (the link no longer points to what it originally pointed to). A little more whimsical would be to use the word breadcrumb:

| It's not a shortcut, it's a breadcrumb.

This would imply the web link merely takes you to a starting point to find the true thing of interest, rather than taking you directly to the thing of interest. However, it is kind of an abuse of the term, since in computer jargon, it refers to the collection of "back links" that the browser tracks for you so that you can back your way out to your starting point.