Well I just googled Firefox and not loading background tabs is the default setting of the program.
"When you restart Firefox and restore your previous session, Firefox will wait until you select a tab before loading it. This keeps Firefox running quickly and smoothly."
https://support.mozilla.org/en-US/kb/allow-firefox-load-multiple-tabs-background
And they are right. So that's an option.

Removing "extended lazy session" was the stupidest idea. Or not implementing it permanently if you so prefer.... On older machines using too much RAM is an obvious fault. But even on my gaming comp, where i would run a browser along with a high performance game it's eating up my RAM. Not to mention my friends case, where he has a limited net contract, and loading every currently unused tab each time he opens Opera is insane. And stupid suggestions like don't keep tabs open or don't run browser in the background or buy even more RAM are not helpful. Why would I have adapt to a program that is performing worse than it did before. I too have been using opera for 10 years or so, but it seems I have to look for an other browser, the can perform this really simple task of not loading background tabs.

Removing "extended lazy session" was the stupidest idea. Or not implementing it permanently if you so prefer.... On older machines using too much RAM is an obvious fault. But even on my gaming comp, where i would run a browser along with a high performance game it's eating up my RAM. Not to mention my friends case, where he has a limited net contract, and loading every currently unused tab each time he opens Opera is insane. And stupid suggestions like don't keep tabs open or don't run browser in the background or buy even more RAM are not helpful. Why would I have adapt to a program that is performing worse than it did before. I too have been using opera for 10 years or so, but it seems I have to look for an other browser, the can perform this really simple task of not loading background tabs.

Well I just googled Firefox and not loading background tabs is the default setting of the program.
"When you restart Firefox and restore your previous session, Firefox will wait until you select a tab before loading it. This keeps Firefox running quickly and smoothly."
https://support.mozilla.org/en-US/kb/allow-firefox-load-multiple-tabs-background
And they are right. So that's an option.