MacBook Air 2019 is slow, overheats with a loud fan, and crashes frequently.

From your Etrecheck Report " Antivirus software: Apple and CleanMyMac "

Part 1 of 2 — The Risks of Third-Party System Utilities

Any third-party application that interferes with the normal operation of macOS has the potential to turn a perfectly functioning Mac into a serious troubleshooting nightmare.

One important point needs to be understood: An application being available in the Apple App Store does not automatically mean it is safe, necessary, or beneficial to your Mac.

Its presence in the App Store simply means that the developer has met Apple's requirements for distribution through that platform. It should not be interpreted as a guarantee that the application will improve your Mac's performance, protect your system, or operate without unintended consequences.

Ultimately, the responsibility rests with the User to investigate what an application actually does, what level of access it requires, and what changes it makes to macOS before deciding to purchase or install it.

Just because an application is available doesn't mean it belongs on your Mac.

Part 2 of 2 — Dealing with CleanMyMac (aka "BrickMyMac")

When it comes to dealing with the aftermath of CleanMyMac, there are essentially two schools of thought.

The following recommendations assume that the offending application has already been completely removed, following the developer's specific uninstall instructions.

Option #1 — Reinstall macOS Over the Existing Installation

Some contributors recommend restarting the Mac in macOS Recovery and choosing to reinstall macOS over the existing installation.

The intention is to replace damaged or missing macOS system components while preserving the existing installation and User Account.

However, there is an important limitation: Reinstalling macOS does not necessarily repair damage within the Home Folder (User Account).

If the offending application has removed, altered, or corrupted files outside the macOS system installation, those problems may remain.

In other words, this approach may resolve the issue, but there is no guarantee that it will restore everything to its original condition.

Option #2 — Erase, Reinstall and Start Fresh (My Recommendation)

Then there are other contributors — myself included — who favour a more definitive approach.

Rather than attempting to repair an installation that may already have been compromised, I would recommend starting with a completely clean installation of macOS.

For an Intel-based Mac, follow Apple's official instructions:

1. Use Disk Utility to erase an Intel-based Mac
2. How to reinstall macOS

Once macOS has been reinstalled, set up the Mac as a new computer.

Install your required applications individually, obtaining them directly from the Apple App Store or, where appropriate, directly from the software developer.

With one possible exception: CleanMyMac.

I would strongly recommend leaving it out of the equation.

An Important Word of Caution About Migration Assistant

If you choose the clean-install route, I would also recommend NOT using Migration Assistant to bring everything back from your Time Machine backup.

Why?

Because if the backup was created while the offending application was installed, there is a very real possibility that migrating the existing environment could reintroduce the same problematic files, settings, extensions, or other components that contributed to the original problem.

In effect, you could go through all the trouble of erasing and reinstalling macOS, only to bring the original problem right back.

Instead, start fresh and selectively restore your personal documents, photographs, music, and other data. Reinstall applications individually rather than migrating the entire previous system environment.

My Bottom Line

If an application has interfered with the normal operation of macOS, my preference is to eliminate any lingering uncertainty rather than gamble on whether an over-the-top reinstall will fix everything.

A clean installation, followed by carefully selected data restoration and fresh application installations, provides the best opportunity to return the Mac to a known-good operating condition.

Sometimes, starting over is considerably more efficient — and ultimately more reliable — than trying to repair damage you cannot fully identify.

Some more specifics:

— Among the useless-ware is Piriform Ccleaner. It's no better than CleanMyWallet.

— You are not yet out of hard drive space but that tiny 256GB SSD fills up fast. The more crowded the drive, the slower your performance.

— Your drive scores are horrible:

Performance:

System Load: 36.98 (1 min ago) 65.74 (5 min ago) 40.60 (15 min ago)

Nominal I/O usage: 0.68 MB/s

File system: 46.52 seconds ⬅

Write speed: 375 MB/s ⚠️⚠️⚠️

Read speed: 1582 MB/s ⚠️

Your Write speed should be close to the Read speed, but yours at 375 MB/sec is almost as slow as an old-school mech hard drive! And even 1500 for the Read speed seems slow. I'm accustomed to expecting 2000-2500 MB/sec reads for that SSD model. Your bad drive speeds alone could account for the feeling that the computer is slow.

I like to see File System under 30 seconds.

The Deal: A "cleaning" app WILL reduce drive scores reported byEtrecheck. You have TWO cleaning apps!!

To Do; AFTER evicting the scammy cleaning apps, rerun EtreCheck and see if those drive score numbers increase. If not, and before doing a reinstall, try a Safe Mode Boot. When I've seen depressed Write speed scores on my SSD-equipped Macs, a Safe Mode boot corrected it. But you have to give Safe Mode time to work.

After achieving a Safe Mode Boot (Start up your Mac in safe mode - Apple Support), let the computer sit unused in Safe Mode for 20-30 minutes before doing a normal startup. That gives time for Safe Mode to do its housekeeping. Recheck scores.

— This:

Top Processes Snapshot by CPU:

Process (count) CPU (Source - Location)

Google Chrome Helper (Aperitif Renderer) (8) 32.22 % (Google LLC)

Google Chrome Helper (Aperitif) (5) 26.32 % (Google LLC)

WindowServer 23.62 % (Apple)

Google Chrome 11.58 % (Google LLC)

EtreCheckPro 9.96 % (Etresoft, Inc.)

'Nuff said. Other browsers are much less hoggish of hardware resources.

— SilverLight and Flash Player have been dead for several years. Let them go.