I'm always reading comments like "Pfff, even Ancients today would stomp pro players back then" or similar stuff, but people only focus on how supposedly everyone has gotten better. Sure, that's true, but honestly, the game has gotten a lot more forgiving as well, along with some major power creep. Just a few examples:
Regen stuff like Salves and Clarities used to get cancelled by creeps. You used to have to be very careful with how and when you used them. Nowadays you can just use them without worries.
Heroes used to have way less efficient skills. Take Wraith King for example, his skeletons allow him to farm a lot faster. He didn't have that, it was just a normal lifesteal.
Heroes have overall gotten a lot tankier. I watched a game where a Mushi Storm Spirit had BKB and Linkens and was lvl 20, he had 1400 HP. Nowadays, Storm Spirit can easily get to 2K+ hp pre lvl 15.
Single courier for everyone, no free items shipped to you in lane all the time.
No backpack, no dedicated slot for TP scroll. 1 slot in your inventory was always reserved for TP scroll.
There is much more, but you get the picture. To be clear, players have definitely gotten a lot better at the game, but we should also keep in mind that compared to now, you had way less tools at your disposal.
Source: https://www.reddit.com/r/DotA2/comments/11nkllm/ive_been_rewatching_some_older_pro_matches_and/