Is publishing a paper only with theoretical knowledge deemed okay? I was invited by an editor (through a lecture series) to publish a paper in an Urban Planning journal. I wrote two articles and they're published recently. However, I don't feel proud instead I'm self criticising and feeling that my work is not up to the standard ( I mean more research and analysis). A theoretical analysis was done but I'm somehow not convinced that I did a good job. Is this normal? Am I just feeling the imposter syndrome? I'm a Masters Student in the final year and I want to do a PhD and get into academia.
Actually, if the journals that published your work are reputable, then you are definitely "up to the standard". So, yes, it feels like a bit of imposter syndrome. And maybe the shock of early success (which is far preferable to the opposite).
Talk to an advisor about how "theoretical" work is accepted in your field. The journals who welcome it might be different from those with a more practical focus.
If you don't already know about the quality of the journals you've published in then a local professor can give you advice on that as well. But from a distance, all seems good.
From my experience, it is difficult for a master's student to evaluate the quality of academic journals and of the articles published in them (including their own). I echo Buffy's recommendation that you should talk to a professor to get their assessment.
However, I would add the strong emphasis that it is usually (though not only) researchers who actively publish themselves who are able to give you a reputable assessment of the quality of the journals in which you have published. So, I would recommend that you search a researcher's research record first on Google Scholar to make sure that they are themselves actively publishing researchers in the field of Urban Planning. When you have verified that this is the case, then you can ask such a researcher their honest assessment of the quality of the journals in which you have published. (And even better, if they have the time to give you, they could even take a look at your articles to assess their specific quality.)
My implication is that if you ask a professor who is an inactive researcher about the journals, they might say that it is great just because they themselves do not actively publish that much.