I have some experience with this unintended negativity, both from working on my own and helping friends and colleagues (programmers). You care and want to help - feeling positive or neutral, people feel like you are pushing negativity on them.
I'm happy to have a longer discussion with you over DM to help - maybe go through some conversation examples - but for general advice I'd focus on:
Suggesting improvement is criticism.
When talking about non-persons (plan, initiative, item, map, game, ...) people will take it personally if they have any connection to it. E.g. if they found a new gun, they may be excited to test it out. Commenting "x is better" sucks away their happiness. If they have spent a lot of time grinding on something, telling them "you should do Y it is faster" devalues the time they spent and makes them feel stupid.
Most people you interact with don't want to play optimally. Any helpful advice to show them a better way is making them feel worse about the fun they are having.
But! If people ask you for advice explicitly, let loose! What would otherwise be interpreted as negativity, will be taken positively.