IMO, yes learn the tunes with no ornaments, so that your rhythm is spot on, all the while thinking of different ways to ‘say’ it , phrase the tune. Some players and regional/personal styles ornament little to none, concentrating on a driving rhythm and lift strong enough to get yous flying!. The only reason you find it hard to ‘put the ornaments in’ is because you dont really know the tune. Once you can play it then IME you will find you naturally express yourself with ornaments, they fall off the fingers.. .
Ornaments are simply that, they are what you can choose to do once the structure is internalised.
There is an approach, as typified by the British military pipe band tradition of learning tunes with set ornaments. However this is contrary to the Gaelic spirit which is exemplified by the Irish tradition of personal interpretation and to be honest it does seems only few pipers really are able to approach a high level with this approach, and it can leave little room for personal expression. I am a great fan of GHB music, the level some players achieve is remarkable, John Burgess, Jim MacGillivray to name but 2.
The approach of learning the tunes, with integral ornaments is however , IMO, limited, there seems little option to vary those ornaments as we would in Irish music, one time a cut, another a roll, third time a plain note, 4th a slide, fifth triplets etc etc etc its all by the book, regimented, controlled, the power is with the judge, the written record, Historically the performers have been to some extent disenfranchised by the ruling class, those with the money to control.
It does seem that there has been to some degree standardisation within Irish music as well, but it really is contrary to the very ethos underlying the art form; that of personal expression, creation, within and even without the boundaries of the form.
It is quite acceptable to play the tunes without ornaments, with lift and drive. Its dance music, it serves a purpose as part of a communal activity. Sadly this has been lost in some places but luckily not everywhere. A tune with all the ornaments and frilly bits without the ‘solid centre’ is of little use to a dancer.IMO You really need to be able to stand alone and play for the set dancers. if you cant do this you need to learn to. Precise accurate rhythm, drive and lift. once you have these, once you have power in your playing, then sure go ahead ornament to your hearts content, but not to the exclusion of the rhythm.
Listen to the old fellas, try clarebannermans you tube for classic stuff.