Repository: create-react-app
Issue: running create-react-app with npx unexpectedly installs create-react-app via yarn
Labels: needs triage,issue: bug report

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### Describe the bug

by using NPX it implies that the user wants to use NPM, however create-react-app forces the zucc onto the users with yarn anyway.

### Did you try recovering your dependencies?

Yes. This does fix the issue. But that's not the problem. The problem is that by using NPX it implies that I want to use NPM. If i were using yarn I would be using `yarn create react-app`
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### Which terms did you search for in User Guide?

I searched for issues that are like this but I couldn't find any.
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### Environment

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  Run the following command in your React app's folder in terminal.
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```
  current version of create-react-app: 4.0.3
  running from /home/alice/.npm/_npx/9475/lib/node_modules/create-react-app

  System:
    OS: Linux 4.4 Ubuntu 18.04.4 LTS (Bionic Beaver)
    CPU: (24) x64 AMD Ryzen 9 3900X 12-Core Processor
  Binaries:
    Node: 12.16.1 - ~/.nvm/versions/node/v12.16.1/bin/node
    Yarn: 1.22.4 - /usr/bin/yarn
    npm: 6.14.4 - ~/.nvm/versions/node/v12.16.1/bin/npm
  Browsers:
    Chrome: Not Found
    Firefox: Not Found
  npmPackages:
    react: ^17.0.1 => 17.0.1
    react-dom: ^17.0.1 => 17.0.1
    react-scripts: 4.0.2 => 4.0.2
  npmGlobalPackages:
    create-react-app: Not Found
```

### Steps to reproduce

```bash
npx create-react-app thisbug
cd thisbug
npm i express --save
find node_modules/.bin -type l ! -exec test -e {} \; -print # detects broken symlinks. output: node_modules/.bin/node-which
```
### Expected behavior

I expect it to use NPM to install. Yes I know there is a `--use-npm` flag, but that is beyond the point.

the find command returns no output, implying there are no broken symlinks


### Actual behavior

node_modules/.bin/node-which is a broken symlink.

Yes I understand that this is a compatibility issue with npm and yarn.. specifically on ubuntu (not a problem on windows), however, rather than taking this up with NPM I think it's better to blame create-react-app as  yarnpkg was not expected to run in this situation as npx is provided by npm.

note this screenshot was taken after running `npx create-react-app thisbug &&  cd thisbug` then `npm i express --save`
![image](https://user-images.githubusercontent.com/1855905/109350706-37d15e80-7835-11eb-8ac5-ed8cd8b704be.png)

(Write what happened. Please add screenshots!)

### Reproducible demo

```bash
npx create-react-app my-app

# installing via yarnpkg
```