It's a tough one for me, honestly, and so this is going to be a long post. I think I'd say that personally I enjoyed airsoft the most around when I started in 2004 up until about 2010 when I took my first break. The VCRA was a bit of a kick in the nuts, but it wasn't the end of the world, but I remember game days fondly from back then. However, I'll be talking about the reasons why the modern day is still good. Airsoft is a constantly evolving thing and that comes with both positives and negatives. Anyway, I'll list the reasons why 2004 - 2010 was my golden age:
Social media wasn't as prevalent. This is THE big one for me as social media breeds a lot of what's wrong with airsoft these days. Whether it's people like Kicking Mustang making yet another "I RUIN NOOBS DAY WITH SAVAGE HEADSHOTS FROM OVERPOWERED PISTOL" video, or the milsim-elitist-geardo crowd showing off their ridiculous loadout with real NVGs and a thermal imaging drone and real-steel everything and telling you, directly or indirectly, that your gear is shit (you know the types). I think social media is the root of a lot of negative things, not just with airsoft but that's a discussion for another time
I never had anywhere near the number of issues back then than I did today, with the only glaring example being when a bunch of guys from the year below us at school decided to come to a game day and rampantly didn't take their hits, but they didn't last long and after another game day or two they were completely gone. We were slinging .2s and *maybe* .25s if you were going heavy, but people still were able to take their hits reliably.
It was a bit more trustworthy. Nobody chrono'd (and I'm not saying we shouldn't, definitely think it's needed these days), but we didn't really need to as there were never really any issues with people running hot guns or people getting injured (unless they came out of the box hot, which some did, but even then I don't remember seeing any injuries). I know my Dboys m4 was about 390fps out of the box or something, and I had a Warrior L96 sniper rifle without a sidearm, but I never full-auto'd people up close and never took shots within my MED. Similarly, I never had any issues with someone running some stupidly hot gun and injuring people.
When I played in Spain between 2008 - 2010 (probably my absolute favourite time playing and my true "golden age") we didn't even have marshalls as "official" airsoft sites didn't exist at that point; we just showed up to abandoned urbanisations, of which there are a LOT on the south coast of Spain, and played BB wars and it was a LOT of fun. We also hired the land next to a hotel (and booked a lot of rooms at the hotel) for a weekend event and it still remains my favourite event I've ever been to; again, we had no marshalls, we had some players who organised what the games would be and the objectives and we just had fun.
As you said, it was a mostly even playing field. There were some guns that were just... really good, but even fine tuning guns didn't create such a divide. The best guns I remember from back then were... A sniper on the team I was a part of had a Tanaka m700 or m40a1 or a TM VSR-10 (can't remember exactly, but it was one of those) which he had tweaked a whole lot, two German guys in Spain had KJW m700s that they had tweaked and my Cyma m14 SOCOM were the ones that immediately come to my mind.
Less ghillies. I know, me, a bush wookiee, complaining about ghillies, but they're bloody everywhere now. Back then we didn't have anywhere near the number of them and if you wanted one you had to make it. I still remember as a 17 year old going to a fabric shop and buying a bunch of burlap, dyeing it three different colours in a bucket on the outside terrace in the Spanish townhouse we lived in at the time, and then tying it onto a Webtex concealment vest, supplementing it with natural foliage on the day. Nowadays, anyone can just buy a Novritsch rifle and a KMCS and be done with it. I don't think that's a bad thing (development and offering more products is generally good) but I think combined with the social media point it's making a lot of players play timid.
Guess I should touch on that as well. People weren't anywhere near as... fragile(?) as they are now. People flung themselves into games and had a laugh when they got lit up, but nowadays it feels like everyone sits out of range of each other just spraying BBs at barricades. Also, if you hit someone with more than a single BB, there's every chance they're going to throw a hissy-fit over "overshooting" because 5 BBs hit them. It's part of the reason I'm ditching my ghillie for the next few game days at least, to see if I can galvanise some activity.
However, I would also argue that today is the golden age:
There are a LOT more players nowadays. A "very busy" day in my golden age was like... 30 players. Now, you're looking at over 100 at my local site and I know some get even more. New blood in the hobby keeps the hobby alive
The sheer range of internal upgrades and how effective they are. Getting a 1.1J build to shoot accurately to 60m is pretty simple these days, where getting a bolt action to shoot 60m back in my golden age would've been considered witchcraft. I think my Cyma m14 SOCOM was a DMR at 420fps (1.6J) and it probably fired to 50m(ish)
Accessibility for newer players. As I said when I was moaning about there being too many ghillies, it's incredibly easy for people to get into the hobby and do what they want. This is definitely a good thing and contributes to the hobby having a healthy player count.
The guns are way higher quality than they were. Back then, you either paid a LOT for a TM, Tanaka, Systema etc, or you bought a Cyma that would probably break because the externals were made of pot metal, or you bought something where the internals would crap themselves after a small amount of use.
Gear is way higher quality than it was. I remember Viper gear was utter shite back when I first played, so like with guns you either paid for some expensive Warrior Assault Systems kit, or you bought a Viper rig that fell apart. Nowadays, I have nothing against the repro brands like Viper or 8fields and have a lot of their kit; it's sturdy and does the job at a fraction of the cost, though I will always love my WAS stuff, since I still have the chest rig I used in Spain and it still works just fine and shows no sign of breaking any time soon.
I'll stop waffling any more than I already have. TL:DR, 2008 - 2010 was my golden era when I was living in Spain, though that's also partially down to the sites we played at!