1st: we've always been a defense oriented organization. It's part of our culture. That will always make it harder to allocate resources to our offense. See Ngakoue. It was no problem no trade for him - don't get me wrong I liked it as well - but we don't have a Mason, Boldin, Smith Sr. type of player right now. This means Roman, Culley and Urban have to become creative. Find ways to get the ball out quickly. We can no longer force the defenses to play according to our offensive personnel -> adjust and look what other teams run and steal from them. Play to the strength of our current WR corps. Force zone coverages and they should better trust the young guys now.
So on the offense/defense blend...
It's merely just a product of talent and resources. Most of the young talent on the roster is on the offensive side of the ball (Lamar, Dobbins, Edwards, pretty much the entire Oline, Andrews, Brown, etc.). So the reality is making any significant veteran investments in the offensive won't yield much, because you have upwards of at least 6-7 players on the offense that, when healthy, are starters and won't be replaced by veteran talent.
Meanwhile, on the defensive side of the ball, you have very little, or any, impact players on rookie contracts. Veteran, aging, defensive line, pretty much paying veteran prices for almost all of our secondary except for Elliott, you're paying market values for pretty much the entire pass rush group. The only position we have rookie-level youth is at LB, seemingly, and that investment is merely like 6 months old at this point.
If we didn't have so much cheap talent on the offensive side of the ball, we wouldn't be investing most of our FA resources on a defense that's getting older. As others, including myself, have indicated, expect this to almost completely reverse within the next probably 2-3 years. As Guys like Stanley, Brown(s), Lamar, Andrews, etc. come up for their first big paydays, they'll be getting more of the money, and the defense will shift towards youth and draft picks. Its a balancing act.
As it were, its sort of amusing and not just a little hypocritical of the fanbase to complain about lack of veteran talent/investment on offense, especially at receiver. We did nothing but ignore the position in the draft for like a decade, and just put band aid after band aid on those resources. And now when we do bring in guys like Brown, Andrews, Boykin and Hurst, we now complain about lack of veteran additions or upgrades. I'm not suggesting these guys are alpha world-beaters, but its not for lack of effort in the draft towards upgrading these positions.