TEFL/TESOL abroad at university or adult ed level: still doable without a CELTA?

[EliEverIsAHero]

Many years ago, when Fred Flintstone was still alive, I did 2 TEFL/TESOL certificates. These have served me well for teaching English to foreigners, adults and children online, but when looking at the market for physical classroom teachers, it's very difficult to avoid postings for teaching children: which, speaking for myself, I don't feel particularly well-calibrated to do; classroom management is more difficult, for one thing, versus adults who want to be there, are eagerly pursuing a language requirement to finish a Bachelor's or certification, or have a professional interest in learning. 

The market for teaching adults (ESL) however, is dominated by requirements for a CELTA/DELTA. Is it still feasible to teach ESL to adults with a TEFL/TESOL certificate, or is it necessary to bite the bullet and spring for a CELTA, even though that seems like overkill?

[EliEverIsAHero]

I should have clarified in the original post that this thread was intended to specifically be about teaching ESL. I wrote this in a relative hurry and unfortunately the not-very-exact title reflects this.

[Jonathan Whatley]

I should have clarified in the original post that this thread was intended to specifically be about teaching ESL. I wrote this in a relative hurry and unfortunately the not-very-exact title reflects this.

No problem, I edited the title to specify TEFL/TESOL!