Error message when passing Plugin class in rx.Config is terrible

[masenf]

Describe the bug

import reflex as rx

config = rx.Config(
    app_name="repro_sitemap",
    plugins=[
        rx.plugins.SitemapPlugin,
        rx.plugins.TailwindV4Plugin(),
    ]
)

To Reproduce
Any plugin in the list that is not an instance will trigger the following exception:

Traceback (most recent call last):
  File "/Users/masenf/code/reflex-dev/repro-sitemap/.venv/lib/python3.14/site-packages/reflex/utils/prerequisites.py", line 351, in 
compile_or_validate_app
    get_compiled_app(
    ~~~~~~~~~~~~~~~~^
        check_if_schema_up_to_date=check_if_schema_up_to_date,
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        prerender_routes=prerender_routes,
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    )
    ^
  File "/Users/masenf/code/reflex-dev/repro-sitemap/.venv/lib/python3.14/site-packages/reflex/utils/prerequisites.py", line 270, in get_compiled_app
    app._compile(prerender_routes=prerender_routes, dry_run=dry_run, use_rich=use_rich)
    ~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/masenf/code/reflex-dev/repro-sitemap/.venv/lib/python3.14/site-packages/reflex/app.py", line 1478, in _compile
    _submit_work(
    ~~~~~~~~~~~~^
        compiler.compile_root_stylesheet, self.stylesheets, self.reset_style
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    )
    ^
  File "/Users/masenf/code/reflex-dev/repro-sitemap/.venv/lib/python3.14/site-packages/reflex/app.py", line 1466, in _submit_work
    f = executor.submit(fn, *args, **kwargs)
  File "/Users/masenf/code/reflex-dev/repro-sitemap/.venv/lib/python3.14/site-packages/reflex_base/environment.py", line 615, in submit
    future_job.set_result(fn(*args, **kwargs))
                          ~~^^^^^^^^^^^^^^^^^
  File "/Users/masenf/code/reflex-dev/repro-sitemap/.venv/lib/python3.14/site-packages/reflex/compiler/compiler.py", line 191, in 
compile_root_stylesheet
    code = _compile_root_stylesheet(stylesheets, reset_style)
  File "/Users/masenf/code/reflex-dev/repro-sitemap/.venv/lib/python3.14/site-packages/reflex/compiler/compiler.py", line 260, in 
_compile_root_stylesheet
    for sheet in plugin.get_stylesheet_paths()
                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~^^
TypeError: Plugin.get_stylesheet_paths() missing 1 required positional argument: 'self'

Expected behavior
we should probably do one of two things in the framework though:

1. error if the user does not pass an instance of Plugin
2. try to create an instance from a Plugin class by passing no arguments

Number 1 is the most philosophically pure: use the API correctly or it doesn't work at all. Number 2 would be more along the lines of the old reflex philosophy.

Specifics (please complete the following information):

• Python Version: 3.10+
• Reflex Version: 0.9.1
• OS: any

Additional context
Any fix should add tests and make sure to implement the validation for this plugin checking in a reasonable place: it shouldn't happen every time a plugin is invoked.

[linear]

ENG-9449