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I use macro extensions on a daily basis on my 18-55mm standard Canon lens.
I tend to take a lot of macro shots, and was wondering whether a telephoto, for example, wouldn't be a better suited lens to use.
(I haven't gotten my first telephoto lens yet.)
I think you need to step back a bit here as you seem to have a misunderstanding or two. Most importantly, a telephoto lens will not necessarily give you better macro capabilities than a normal lens. For example, the Canon 18-55 IS STM has a maximum magnification of 0.36×, while the Canon 55-250 IS STM has a maximum magnification of only 0.29× - ie the "equivalent" telephoto lens has less macro capability than the normal lens. Telephoto lenses do have some advantages for macro work, principally that the lens is further from the subject so it's easier to get your lighting set up, but macro capabilities are not intrinsically one of them.
Now we've worked out that a telephoto lens isn't necessarily what you want, the question is "what do you want?" The answer here is actually fairly simple: a dedicated macro lens. Canon make a couple of reasonably priced macro lenses (EF-S 60mm, EF 100mm) and there are also third party manufacturers which give other options. Both the Canon lenses give you "true macro" (i.e. 1:1) reproduction. If you want to go further than that, Canon make the very specialised MP-E 65mm which will give you 5× magnification, but definitely do some reading before buying the lens as it's got a lot of quirks.
The macro lens is best for close-up work.
Most close-up subjects are shallow as to their depth. The macro lens is optimized to handle a flat subject and project their image on the flat surface of film or sensor. The standard camera lens is optimized to image a curved world and project that image on a flat surface. We often reverse the standard lens; this allows the back focus, optimized to work on a flat surface, to image the subject.
As we close focus the f/numbers engraved on the lens barrel become invalid. As we approach “unity” (life size or 1:1), the error is two f/stops. This error called bellows factor is responsible for a high percentage of under-exposures. This is moot if the exposure is measured thru-the-lens. Nevertheless, one great attribute of the macro is, the f/numbers remain valid.
All lenses are degraded by uncorrected aberrations. The standard lens is optimized for distance work; the macro is optimized to work at “unity” (life-size).
The standard lens when tasked to make close-up images has better acuity if reversed. This deed disconnects the electrical connections lens-to-body. This forces the photographer to make manual lens settings. The macro remains attached to the body thus the full automation of the camera remains unbroken
