Sometimes this type of question is very difficult to be answered in a manner that everybody find it good enough. I will try to give you my opinion on this issue.

There are two types of researchers. One that works alone and in this case he/she will do all the work related to the preparation of an article or articles on the research he/she is doing. The second is a researcher that works in a team and he/she is the team leader. In this specific case, what should be his/her role? In this case the role of the researcher as a team leader is to identify a specific idea or ideas of what kind of article or articles should be prepared in relation to the research that the team is carrying out. He/she should also define the structure and the main content of the article or articles to be prepared and what are the individual responsibilities of each member of the team. The most senior researchers working with the team, if there is any, should be in charge of writing the first draft of the article or articles following the guidance of the team leader, At the same time, junior members of the team should be in charge in searching for data, references materials, former researches carried out before on the same subject and their main conclusions and any other support tasks that the team leader consider appropriate to give them, according to their experience and results of their work in the team, among other factors to be considered.

The team leader should have full and unique responsibility of the final content of the article or articles that have been prepared by the team under his/her supervision, and should decide which are the members of the team that can be considered as authors and which as co-authors. This decision should depend, in my opinion, on the role played by each member within the team and the work done by each of them during the preparation of the drafts of the article or articles that have been prepared.

I am aware that sometimes team leaders play almost no role in the preparation of an article, and yet he/she will appear as the main author of the paper prepared. This is something that depends almost exclusively on the professional ethics of the team leader.

In my view, a "team leader" should only be an author IF he/she has contributed significantly to the work. Providing financial support (e.g., paying a post doc's salary), funding the project,  or providing the lab space does not entitle one to an authorship.

Many years ago (back in the 80s), I published a paper with a co-author who really had had no input or involvement in the work. I hoped he/she would recognize this and suggest their name should be dropped. They didn't and I found I was in an awkward position (he/she was senior to me). After that, I decided it would never happen again.

I have a strict rule: to be an author, one must have contributed significantly to the work. Collecting and analyzing data under my supervision does not automatically make one an author; however, if that person also does some writing (e.g., a draft of Methods), then they may be an author. In the case of students/post-docs, I almost always have them as first author, provided they worked on the writing (in addition to their work with me on study design and, of course, their carrying out the study).

Please see my challenge on the dominance of the ICMJE, and the ethics of so much power:

https://www.researchgate.net/post/Is_it_ethical_for_the_International_Committee_of_Medical_Journal_Editors_ICMJE_to_have_so_much_power