I don't know much about .bst files; however, a cludgey way to get rid of the doi (and other urls) in the aasjournal bibliography style is to change the following commands from:
"\providecommand{\url}[1]{\href{#1}{#1}}"
write$ newline$
"\providecommand{\dodoi}[1]{doi:~\href{http://doi.org/#1}{\nolinkurl{#1}}}"
write$ newline$
"\providecommand{\doeprint}[1]{\href{http://ascl.net/#1}{\nolinkurl{http://ascl.net/#1}}}"
write$ newline$
"\providecommand{\doarXiv}[1]{\href{https://arxiv.org/abs/#1}{\nolinkurl{https://arxiv.org/abs/#1}}}"
write$ newline$
to
"\providecommand{\url}[1]{\href{#1}{#1}}"
write$ newline$
"\providecommand{\dodoi}[1]{}"
write$ newline$
"\providecommand{\doeprint}[1]{}"
write$ newline$
"\providecommand{\doarXiv}[1]{}"
write$ newline$
In my copy of the file, this begins on line 1776. Removing the newline$ commands from the file won't change the line spacing.
To change the spacing in the bibliography, the natbib package has a useful command to change the separation between bibitems (see this Stack answer). If using aastex, I believe natbib is already loaded.
\usepackage{natbib} % skip if already loaded
\setlength{\bibsep}{2pt}
To completely remove the new line and have the entries simply listed, there is a solution which works with aastex on {TeX|Stackexchange} here. Commenting out the two \printfield commands will remove the added line numbers. This will override the aasjournal.bst style.
\setlengtheach bibitem starts on a new line, which is precisely what I don't want. I'd need all items to be continuous like text. Do you also know how to add "et al." for more than two authors? – Py-ser Dec 18 '21 at 15:04.bstfiles, but you can lookup how to modify biblatex styles. A jumping off point with would be this useful post. – J.L Dec 20 '21 at 00:13