I don't doubt that there are more mods now that there were in the past, but that's because the number of games and players has skyrocketed in the last few years, as well as the number of game developers (who often start out modding). That doesn't mean it's not harder.
Back in the 90s and early 00s for example most games were made by a small handful of people and were relatively simple and self contained, and could realistically be reverse engineered even if there were no official tools. Most of the overhaul mods from back then were made by one person.
Yeah dont go there mate, been playing games since the 1980s and not many people could mod before 2005 without any coding skills at all. Today, anyone can mod if the game has either official tools, professional tools the games use (like unreal), or player made tools released to the public. And then there are games now, made by experienced programmers with modding in mind like the previously mentioned Empyrion Galactic Survival (this is a survival combat game with a hint of NMS in it with a large randomly created galaxy in it that can have over 10,000 star systems) that just with Notepad++ and a little knowledge of how the game is laid out, you can mod all the basics (in Notepad++) because they MADE it to be modded easily. A bunch of .ECF files with basic game information for items/creatures/blocks and then .YAML files that handles all planet data, temperature, graveity, what life/items appear and how many, planetary objects like trees, rocks and all colors associated with it, all editable...with more files that alter how many planets, star systems...you name it, it can be edited and to create a new kind of existing creature all it takes is a simple copy/paste into the correct files and assigning an ID that is opened and creating/adding a loot list for it and if you want a brand new one, only requires creating a new skin to be created and exported to BMP and placed in the right folder and have your new creature call to it.
No actual programming knowledge required...in fact, many games being made with Unity 2018 or later, are easy as hell to mod.
This is a snipit from a planets .yaml file
Seed: 1
PlanetSize: 3
PlanetAxis: 21.54195
TemperatureMinMax: [0, 45]
TemperatureNight: 7
HumidityMinMax: [0.1, 0.7]
SeaLevel: 40
TerrainLevel: 140
BaseLevel: 0
LandWaterRatio: 0.1070294
TemperatureHeightRange: [30, 50]
TemperatureGradientRange: [0.55, 0]
TemperatureNoiseFac: 0.75
HumidityHeightFac: [0, 270]
HumidityNoiseFac: 0.9
Gravity: -10.93
Radiation: 0.0
AtmosphereDensity: 1.4
AtmosphereO2: 0.2
AtmosphereBreathable: True
GroundFogIntensity: 0
GroundFogHeight: 0
AtmosphereFog: 0
PvP: False
Want a larger planet possibility, just change 3 to 4 or 5. Altering planetaxis changes suns rise/set position. Temp max, is clear raise that 45 to 50 for a much higher possible max temperature...you can change water to land ratios, effect of gravity and oxygen...all just by changing some numbers and then clicking the SAVE BUTTON...do not even need to re-cook any files or anything. That is just a TINY portion of this file, everything about a planet can be changed. Even the skys color, color of grass(if there is any)...everything...in a simple file opened in Notepad++. The only kind of better than average knowledge you would need would be if you were wanting to do animations and knowing how to do some graphics design to aid in making new skins faster. The game is so moddable you can create a TEXT FILE for your story and just import it in as long as you added in the correct contextual locations for where the text needs to be placed in the game. And if you want to create every aspect of a planet from scratch, you can do that also with one of several player made tools that does require a slight learning curve but should easily be able to nail it in a day or 4. The game isnt fully released yet, and already has more than a few full player made "scenarios" and over 100,000 player made ship designs on the Workshop.
So sorry to break it to you man, but modding is not limited like it once was. It is prolific and there are far more mods now, because its far easier to mod...not just because there are "more games" that have it and it will continue to expand as more and more companies make games with Unity and Unreal.