I'm at the login screen, type in my user password, hit enter - And am instantly in my desktop.
No wait, no delays.
Only 651 MB of my 16 Gig RAM are used.

How? 

When you install Linux Mint, you use the Cinnamon Desktop. Mint is popular, because this desktop and services feel very much like a modern Windows.
From my activities 20 years ago though I knew, that I don't need all of this on a daily base.

So I installed the LXDE Desktop, and replaced the windowmanager Openbox with Icewm in the settings.

Much better, still 1.3 gig used, this is not normal.
I installed "htop" to check the memory usage.
Turns out, some gnome-evolution services were eating 500 MB.

Deactivated them:

systemctl --user mask evolution-source-registry.service evolution-calendar-factory.service evolution-addressbook-factory.service evolution-user-prompter.service


systemctl --user stop evolution-source-registry.service evolution-calendar-factory.service evolution-addressbook-factory.service evolution-user-prompter.service

Reboot.
Now usage is approx. 800 MB.
The desktop reminds of Windows 95, positively. Light, fast, simple.

I decide, that I don't need desktop icons, either, and Icewm has an own panel, so do not need lxde.

Log out, select "icewm-session".
After some configuration, my desktop looks like on the screenshot, 651 MB used.
The bar on the right are some wmaker dock-apps.

I set the desktop background by opening pictures from the xfe filemanager using this script:
/usr/bin/icewmbg2

#!/bin/bash
pic="$1"
#xmessage "$pic"
sed -i "s#DesktopBackgroundImage=.*#DesktopBackgroundImage=$pic#"  ~/.icewm/prefoverride

icewmbg --center=0 scaled=1 -i "$pic" &
exit 0

If you set this as stardard action to .jpg and .png files, you can switch background via doubleclick.

Here is my ~/.icewm/startup file:

#!/bin/bash
sleep 3
#wmaker dockapps
wmcpuload &
wmmemload &
wmCalClock &
wmfsm &
asmon &
#magnifying glass
#magnus &
#shadows and transparency
compton -c

One issue I encounter with themes in
~/.icewm/themes
is, that they often change "too much".
So I grabbed my favourite setting like fonts and sizes, and copied them to:
~/.icewm/prefoverride

Now the themes basically change only the window decor (titlebar/borders), but not the rest.

To add your own starter icons to the toolbar in the panel, edit:
~/.icewm/toolbar
example:
# This is a default toolbar definition file for IceWM
#
# Place your personal variant in $HOME/.icewm directory.

prog XTerm ! x-terminal-emulator
#prog FTE fte fte
#prog Netscape netscape netscape
#prog    "Vim" vim /usr/bin/gvim -f
#prog    "WWW" ! x-www-browser
prog "Opera" opera opera
prog "Program Manager" thunar thunar "/home/mark/Schreibtisch/Program Manager"
prog "Skippy" xviewer skippy-xd
prog "Screenshot" "gnome-screenshot" gnome-screenshot


So - yes, you will have to edit some textfiles. But it is not complicated as you see.
The result is a very slim and ultrafast system.
And in case I need something from the "big, modern" desktop, I still can switch to that in the loginscreen. But for my daily websurfing I prefer this minimalist approach.