Absolutely! I’ve run 2nd & 3rd edition adventures as well as some pathfinder adventures and they’ve all worked great. Just replace the old stats with new ones when available and when not, just find a close approximation/challenge rating and then use their 5E stats while keeping the original descriptions. Also, with 1st edition in particular, you might need to reduce the number of enemies here and there, but that also depends on your party’s combat ability, so you might have to find the right balance for your group. Over-all I’ve found the 3rd edition and Pathfinder CRs the most helpful for converting to 5E and would recommend them the try first. And as you can probably tell, I’m in complete agreement that the current official 5E adventures are lacking, but we have utterly enjoyed 5E itself. Definitely give some older adventures a try and then let us know how it went.