Why is meteor not installed inside my docker container?

I recently switched my meteor app to use Docker as I am trying to create a new microservice. Previously, I would deploy my app locally using meteor run, but I've switched to docker-compose up --build using a docker-compose.yml at the root of my project and a Dockerfile in my Meteor app's directory. I finally got things running, which is great, but I am now trying to build a dev version and I'm running into some trouble.

In my Dockerfile.dev I am:

1. Setting the node version
2. Declaring Meteor Version and My App's Code Directory
3. Making a /src directory for the container
4. Installing Meteor
5. Copying package*.json files to /src
6. Install npm packages via npm install
7. Copying the My app's source code into /src
8. Setting the working directory to /src
9. Lastly, running the app with meteor run

The dockerfile is running the app, but then my app exits because it cannot find meteor. Which is weird because shouldn't it have to find meteor to start the app in the first place? Anyways, I'm lost and any help would be greatly appreciated. Thanks in advance :)

docker-compose.yml

version: '3'

services:
  myapp:
    build:
      context: ./js/myapp
      dockerfile: Dockerfile.dev
    ports:
      - '3000:3000'
    links:
      - mongo
    environment:
      ROOT_URL: ${APP_ROOT_URL:-http://localhost}
      MONGO_URL: mongodb://mongo:27017/meteor
      PORT: 3000
  mongo:
    image: mongo:latest
    command:
      - --storageEngine=wiredTiger
    volumes:
      - data:/data/db

volumes:
  data:

Dockerfile.dev

# Inspired by: https://github.com/banjerluke/meteor-dockerfile

FROM node:14.17.5 as builder

ENV METEOR_VERSION=2.3.4 \
    APP_SRC_FOLDER=.

RUN mkdir -p /opt/src


RUN echo "\n[*] Installing Meteor ${METEOR_VERSION} to ${HOME}"\
&& curl -s https://install.meteor.com/?release=${METEOR_VERSION} | sed s/--progress-bar/-sL/g | sh

FROM node:14.17.5-alpine as runner

ENV NODE_ENV=dev

COPY $APP_SRC_FOLDER/package*.json /opt/src/

RUN echo '\n[*] Installing Meteor server NPM dependencies' \
&& cd /opt/src \
&& npm install


COPY $APP_SRC_FOLDER /opt/src/

WORKDIR /opt/src/

CMD ["meteor", "run"]

Error

myapp_1  | internal/modules/cjs/loader.js:892
myapp_1  |   throw err;
myapp_1  |   ^
myapp_1  | 
myapp_1  | Error: Cannot find module '/opt/src/meteor'
myapp_1  |     at Function.Module._resolveFilename (internal/modules/cjs/loader.js:889:15)
myapp_1  |     at Function.Module._load (internal/modules/cjs/loader.js:745:27)
myapp_1  |     at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:76:12)
myapp_1  |     at internal/main/run_main_module.js:17:47 {
myapp_1  |   code: 'MODULE_NOT_FOUND',
myapp_1  |   requireStack: []
myapp_1  | }
myapp_myapp_1 exited with code 1