Huh? I had 0 problems upgrading the RAM in my 2011 MBP. Have they made it inaccessible since then?
Unfortunately, yes. Several years ago they started soldering the RAM directly to the motherboard, and don't provide any ram slots. So, whatever amount a unit shipped with is the max it will ever have.
I'm still using a mid-2009 MBP. Upgraded the RAM, replaced the hard drive with an SSD, and just last week installed Catalina on it. It's still my daily driver lol.