Asking the electorate a question is being democratic. When governments lose support and are forced to set new elections early that is a democratic move, not a refusal to respect that they were elected for the duration. The electorate has and will continue to develop and change its preferences and priorities, respecting that is being democratic. Refusing to acknowledge a changing national mood is undemocratic. Polls are indicators, they can be wrong and then the voting results will surprise but the vote will not be undemocratic, regardless of whether the vote was called after a long or short period.
The 2014 referendum was only slightly more decisive than the extremely close 2016 referendum. The Better Together campaigners worked extremely hard to persuade the vote toward them and for a time it was distinctly worrying for them that a Yes vote might end on top. One significant part of the argument against independence has gone in reverse and in Scotland other "promises" are seen as having been forgotten or dumped altogether. In the opening paragraph of the Better Together campaign, it was expressly stated that of course Scotland could make a go of independence - there was no insistence that it couldn't but that Scotland would be better off "together".....as often as not because of habit, respect for the past.
If Scots choose independence in another referendum then that will be because they want it. It will not matter to them if Westminster does not want it. Democracy is not being served if someone tells people that they can't choose what that entity does not approve of.
An independent Scotland would/will fund its own societal elements, just like any other sovereign country. Within the UK Scotland will never be significantly different from the rest - the only way to improve is to be manifestly different, independent. To have a better health service than at present it will only need to improve it to reach, say, 20th place in the world - at that it would be measurably better than the UK's today. If Scotland simply dumps the UK's ways and copies what other countries are doing then it will be set to similarly outperform the UK on pretty much every socio-economic measure.
Why not choose independence ? I am intrigued by how these discussions on AB are dominated by non-Scots who are against independence. I would be surprised if there were not at least a very large number of Scots clamouring for independence.