Look at this:

http://www.lingweenie.org/conlang/gusein-zade.html

Frequencies
Hawaiian etc
7- 29.71, 19.80, 14.01, 9.90, 6.71, 4.11, 1.91
8- 27.47, 18.80, 13.73, 10.14, 7.35, 5.07, 3.14, 1.47
9- 25.58, 17.88, 13.38, 10.18, 7.70, 5.68, 3.96, 2.48, 1.17
10- 23.98, 17.05, 12.99, 10.12, 7.88, 6.06, 4.52, 3.18, 2.01, 0.95

English
19- 15.77, 12.12, 9.98, 8.47, 7.30, 6.34, 5.53, 4.82, 4.20, 3.65, 3.15, 2.69, 2.27, 1.88, 1.51, 1.17, 0.86, 0.55, 0.27
20- 15.22, 11.76, 9.73, 8.29, 7.18, 6.26, 5.49, 4.83, 4.24, 3.71, 3.23, 2.80, 2.40, 2.03, 1.68, 1.36, 1.06, 0.77, 0.50, 0.24
21- 14.72, 11.42, 9.49, 8.12, 7.06, 6.19, 5.45, 4.82, 4.26, 3.75, 3.30, 2.89, 2.51, 2.15, 1.82, 1.52, 1.23, 0.96, 0.70, 0.45, 0.22

Irish
32- 10.93, 8.76, 7.49, 6.59, 5.90, 5.33, 4.85, 4.43, 4.06, 3.73, 3.43, 3.16, 2.91, 2.68, 2.46, 2.26, 2.07, 1.89, 1.73, 1.56, 1.41, 1.27, 1.13, 1.00, 0.87, 0.75, 0.63, 0.51, 0.40, 0.30, 0.20, 0.10

This is a count of how likely any given sound of a language is, and as you can see when there is less than ten, the rate can be near one in three or four for the most frequent (which you would expect to be a vowel like /@/ or /ae/ or /e:/ etc) down to one in six for twenty to one in ten for thirty two.

Now Ive only referenced consonants here (which renders the list odd), but the point stil holds and if you look at Irish, marginal sounds and all, you are looking at, say for example, 60+, so you get:

60- 6.85, 5.70, 5.02, 4.54, 4.17, 3.87, 3.61, 3.39, 3.19, 3.01, 2.85, 2.71, 2.58, 2.45, 2.34, 2.23, 2.13, 2.03, 1.94, 1.86, 1.78, 1.70, 1.63, 1.55, 1.49, 1.42, 1.36, 1.30, 1.24, 1.18, 1.13, 1.08, 1.02, 0.97, 0.93, 0.88, 0.83, 0.79, 0.75, 0.70, 0.66, 0.62, 0.58, 0.54, 0.51, 0.47, 0.43, 0.40, 0.37, 0.33, 0.30, 0.27, 0.23, 0.20, 0.17, 0.14, 0.11, 0.08, 0.06, 0.03

So for rare sounds, they might happen once every 3000 spoken phonemes! At that rate they might drop out unless there was some compelling reason for them to be noticed among natives, let alone learners.

Assuming that a) the eleven monothongs of Irish are the top eleven, and b) the learner is from a language community more sensitive to vowels than a native Irish speaking one, you can see that even the first consonant is less than 3% likely to pop up at any given moment, while the last consonants are under half a percent likely!

This is one way of looking at why the advice to just listen to a language without any guidance can lead to such poor results in articulation and while learning books really need to explain the Irish sound system

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__̴ı̴̴̡̡̡ ̡͌l̡̡̡ ̡͌l̡*̡̡ ̴̡ı̴̴̡ ̡̡͡|̲̲̲͡͡͡ ̲▫̲͡ ̲̲̲͡͡π̲̲͡͡ ̲̲͡▫̲̲͡͡ ̲|̡̡̡ ̡ ̴̡ı̴̡̡ ̡͌l̡̡̡̡.___

Some of the sounds are rare enough alright, I at least needed them pointed out to me.

I really think a careful explanation of broad and slender would help many people get a good footing with the sounds, a native speaker sounding them out seems to work well. Like "bó" and "breá" said slowly and you can hear the differences in the sound. Many of the beginners down in the Adult courses I've seen got a good idea of it out of that.

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The dialect I use is Cork Irish.
Ar sgáth a chéile a mhairid na daoine, lag agus láidir, uasal is íseal

The thing is, languages always have a more-or-less systematic "matrix" of sounds. If voicing is a phonemic distinction in T/D, you can be pretty sure that P/B is a distinction in voicing, and the same for C/G.

If you decompose phonemes into constituent parts, then you can look at the frequency of occurrence of the parts, and all those figures will be higher. I have always felt that a learner should always have some conscious awareness of the pattern of distinctions underlying the phonemes, and then in order to notice an unusual sound, you're just noting a cooccurrence of various familiar elements.

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A language belongs to its native speakers, and when you speak it, you are a guest in their homes.
If you are not a good guest, you have no right to complain about receiving poor hospitality.

Good point.

I think for many people, accent and articulation are wrapped up in identity issues, so you see a reluctance to try to say things right, except when speaking French or similar cases when identification shift (such as some Irish people in the States) is deemed desirable

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__̴ı̴̴̡̡̡ ̡͌l̡̡̡ ̡͌l̡*̡̡ ̴̡ı̴̴̡ ̡̡͡|̲̲̲͡͡͡ ̲▫̲͡ ̲̲̲͡͡π̲̲͡͡ ̲̲͡▫̲̲͡͡ ̲|̡̡̡ ̡ ̴̡ı̴̡̡ ̡͌l̡̡̡̡.___