Gmail has gotten better especially with new additional features. Here are some tweaks you can play around with to get that minimalist look and make your inbox more efficient.
To achieve that simple view, you’ll have to remove most of the clutter such as the text, buttons and retain some features you actually use and couldn’t live without.
Make use of Gmail’s keyboard shortcuts
Gmail has some commands that can be enabled by the keyboard and you can configure them to your preferences. Doing so will remove the need for buttons that clutter the Gmail’s web interface.
Gmail general settings (the gear icon on your top right) > Keyboard shortcuts > click enable > save changes
Once Gmail reloads, go to Gmail settings > Advanced > Custom keyboard shortcuts > click enable > save changes and wait for Gmail to reload.

After Gmail reloads, go to Gmail settings where you’ll see that the Keyboard shortcuts tab has been added along the top bar. From here, go creative with keyboard shortcuts such i to get to your inbox or c for composing a new email or ESC for closing an email.
Minimise Gmail’s left side panel
This means you need to get rid of the text and only allow for icons to save on space
Tap the three-line menu icon that’s found in Gmail’s left side corner on the top to change the panel into a minimal one. The panel will expand if you need to access it by just hovering over it.
Lessen the number of icons Google shows you by default. While on the panel, move your mouse over it and you’ll see More at the bottom. Clicking it will reveal more of your labels and categories for you to see.
If you don’t use the Hangouts Chat down below, go ahead and disable it. Head over to Gmail’s settings and from the tabs, you‘ll see Chat which you can then disable. You can also customize your Inbox view but I just decided to remain with the basics: my inbox, my snoozed emails, my sent emails, my drafts and my all mail. After all this, you can collapse this view by tapping on less to get that less distracting left panel.

Let go of Gmail’s right side panel
Gmail’s right side panel contains links to access widgets like the Keep Notes, Trello and Calendar. There are useful but if you don’t need them at the moment, you can just hide them by clicking the right facing arrow at the bottom right. To access them, just click the arrow which will now be facing the left.
Change your display density
This feature ported from Inbox may be well-intentioned but it puts a lot of clutter to your inbox as it creates large thumbnails for things like attachments.
Go to settings > Display density > select Comfortable view that removes the attachment files

This will give your inbox unified appearance that’s less distracting.
Get Stylebot extension to modify Gmail’s interface
Stylebot is a free CSS-modifying Chrome extension that you can play around for removing some Gmail elements such as margins, the compose button or the Gmail icon.
Removing the Gmail icon can be done by:
Right-click the Gmail icon > select Stylebot > select style element > When the extension’s control panel pops up > scroll to the “Layout & Visibility” section > click the hide button

The same method can be done to the compose button if you’ve already set up a keyboard shortcut for that.

Colour your labels or categories
This will make it easy for you to recognize emails at a glance. Do this by hovering your mouse over each label, then click the three-dot menu icon that is on the side. Select the label colour that will get your attention.
Get a theme
Make your inbox look neater with the right theme. Go to Gmail settings > select themes and scroll over the selections. Once you get one, a theme box will show up. You get to customise the theme such as applying the blur effect or vignette so that you get the same good looking image that will not be distracting in the long term each time you open your inbox.

These are some of the steps you can make to make your Gmail inbox look neat and minimalist while at the same time bringing efficiency to your email productivity.
can it be permanently “Let go of Gmail’s right side panel”? if you hover over it the text still pops up which is annoying, thanks