On Wed, Nov 8, 2017, 7:16 AM Bastien <bzg@gnu.org> wrote:

is there a simple mechanism in Emacs core to restore the same
functionnality?

+1 

I'm aware of Yasnippet, but it is not in Emacs core and it can
be daunting for newcomers to install, customize and use.

I am aware of Yasnippet, have it installed, but haven't used for a long time. The old easy template system just worked and I used it dozens of times a day. 

The previous function was very straightforward and simple, the
cost for losing it seems to high to me.  I'd rather have 10 lines
in Org (and in Emacs core) for it, than to ask users to install
something that does a lot more that they don't need.

I agree with that sentiment. In parallel to removing that feature, it would be needed to add details in the manual on how to restore that functionality using other means. 

Given the lack of time, I just restored for works for me in my personal config: https://github.com/kaushalmodi/.emacs.d/commit/9aa3be89a2f8dce3f2aa57f98e0a2f38fdca4c6b

I just like the convenience of hitting "<s" and let the template insertion logic do its thing. 

Let me know what you think. 
--

Kaushal Modi