I'm going to be honest; I don't believe "this feels modded" is a valid criticism. Regardless of intent, it places an unfair mark of shame on mods as a whole, and if you can back up "this feels modded" with a valid second criticism of an idea, you already had a valid criticism in the first place and didn't need to say it feels modded.
If you have a valid criticism of a suggestion itself, that is fine. If your criticism is that it feels "modded" it has slightly less weight. If you are directly comparing it to an existing mod, and it is something that you don't like, it starts being a very blurry line where you have to ask if you don't like it because it's actually a bad idea or if you don't like it just because you don't like the mod people are referencing.
I'm not for or against anything mod-wise. I don't really mess around with them and the popular ones don't interest me much. Yes, many of them do things I don't personally enjoy. I don't really care since I otherwise don't play them.
Yep! The benchmark of something feeling "modded" changes as the game develops. There's all sorts of things you could point out.
As mentioned, the Aether would have been unheard of in 1.2.4 or 1.3 days. An entire hidden biome with a liquid that changes items? Ridiculous.
Soaring Insignia would have been incredibly polarizing as a suggestion, let alone the UFO mount. Infinite flight? That's way too broken.
Honestly, everything around the Empress of Light. A proper projectile spam boss that instantly kills you during the day? They also drop a bonus item if you start the fight during the day and defeat them! That's insane by 1.2.4 standards.
Moon Lord coming out, then getting Moon Bite a few days later purely to stop lifesteal effects? What kind of modder comes up with this idea? Way to ruin an entire playstyle!
Endless Quiver? No way! Arrows are cheap, prepare better.
Special seeded worlds in general, pylons, then moving Teleporters to post-Skeletron due to Pylons...
Even the modern state of the Terra Blade or the Night's Edge, or the fact we even got the Terraspark Boots at all.
Torch God's Blessing putting down biome torches automatically.
The game has changed a lot over the years. No matter the context around saying it is, to me saying "this feels modded" feels like a cheap pot shot.
Yes, that's the point. I am pointing out things that have happened through the course of normal development that people would say feel modded.
I am also not defending Moon Bite, but it is an example of something somebody would say "feels modded" if the mechanic was not in the game and somebody suggested to give Moon Lord a lifesteal prevention mechanic.