I think there is an important distinction to be made.
There are the eastern european countries willing to join because of protection. Which is understandable, they have more than enough reasons to do so.
There is also the fact that NATO has to accept those countries, which is risky and implies costs for the countries that are already a member. Which begs the question, why member countries would accept eastern european countries? I don't think we are naive enough to think that it's because these states are good guys and want to protect asking countries out of good will. Here's where we need to consider NATO's main goals, historically speaking its very foundation was to check the USSR and preventing them from invading Europe. They also require countries to hold a market economy and a liberal democracy, which means that NATO also has ideological goals to promote in exchange for this mutual defense protection.
So while NATO expands in democratic ways, that doesn't mean it can't be seen as hostile to other countries.
And yes, this doesn't mean that this is the reason Putin is invading, nor justifies it, etc. Not everyone talking about this is shilling Russian propaganda either, here in Latam I've sen plenty of international analysts well outside those propaganda influences talking about this, and about the US' hypocrisy, and also the racial hypocrisy we've seen (how the world seem to care about the war because it's european, how we could be stopping attrocities elsewhere but we aren't, etc.). All of this are repeated talking points, that, while are almost never meaning that these very people support Putin's action, render US' and Europe's statements untrust-worthy.