Many good responses here already - but I'd say that eg choosing between react and vue or svelte isn't an architectural decision. But choosing between server rendered php and react is (is this a series of web "pages" with some forms, or is it an "app"?).

Choosing between mysql, sqlite and postgresql may be (do we need row level security? Would mysql multimaster benefit us? Do we expect to deploy many, small instances where the simplicity of sqlite will shine) etc.

There are many decisions to make building a solution - the architecture part has to do with fulfilling the requirements.

The tech-lead/senior developer/team lead part has to do with implenting the architecture - our team knows vue, so we go with that to implement the app. We're invested in ms sql so we prefer that to postgres - but sqlite would be a poor fit.