Ummm, the Modular was, and is, one of the best engines ever made. Also, the V8 you are alluding to was the Windsor, not the Lima, the Lima engines are V6's. The Modular family has been on Ward's Best list an obscene number of times all the way back to 1996, most recently with the Coyote in 2019.
But you've inadvertently, with the above gaffes, touched-on some of the necessary nuance/details that are oft missed when somebody tries to broad-brush a topic such as this.
The Modular was developed as a "modernized" version of the 427 SOHC, originally under the "Hurricane" moniker. It was designed to improve on some of the weaknesses/shortfalls of the pushrod Windsor, such as the bottom-end, so it featured a deep skirted multi-bolt main configuration along with side bolts.
It was originally a 4" bore design (like the Windsor) but because there were some plans to fit it to a FWD configuration (the Continental) the design was revised and the bore size, and spacing, reduced so that this was possible. The original design was shelved.
The first variant of this engine was introduced as the 4.6L 2V in the Panther cars. The engine was unremarkable. Power was similar to the outgoing Windsor (302). The engine was reliable. It eventually made its way into the Mustang and F-series trucks.
A taller deck height (5.4L) and V10 (6.8L) version were also introduced to provide more HP/torque for truck and SUV applications.
The PI version was introduced in the late 90's, which featured revised pistons (dished), camshafts and cylinder heads that flowed better. However, a design decision was made in order to expedite assembly on both the 32-valve (DOHC) and 16-valve (SOHC) engines that involved more of a "lead" in the spark plug holes so that they would self-centre. This reduced the number of threads that actually engaged the plug (3-4 at the bottom of the hole) and resulted in a situation where, if those threads were damaged, say during a plug change, that one could eject. This was corrected around 2002-2003 when the process was modified to be feature fully-threaded plug holes again.
The 2V modular engines enjoyed a very long production run and had a reputation for dependable service. The million mile Ford van is but one example. The obsession with the panther cars, many which were former LEO, taxi or Limo service tells that story well. An extremely robust powertrain that's relatively simple to work on and will go obscene distances with minimal maintenance.
Along with the 2V modular, its DOHC siblings, mainly the 5.4L in the Navigator, 4.6L in the Continental, 4.6L in the Mustang Cobra and the supercharged variants also saw excellent service. The 4.6L DOHC mill was eventually replaced by the 5.0L Coyote, which was the next generation of this platform.
Somewhere around 2005 Ford introduced the 3V engines which were an SOHC design that had variable cam timing. These engines were designed to improve performance but experienced problems with the phaser system as well as spark plugs that would break-off in the heads, requiring considerable effort to remove. This variant does not have the reputation for reliability of its predecessors. This engine is no longer in production.
Hurricane was eventually renamed "BOSS" and introduced as the 6.2L in the Raptor, eventually making its way into other trucks.
Because not everybody wants a gas-sucking 6.0L engine, so different sizes, which make different amounts of power, are produced to satisfy that need. Same reason Ford produced 4.6L, 5.4L and 6.8L versions of the Modular.
The venerable SBC (5.7L and 5.0L/350 and 305) engines were replaced by better ones, just like with the Windsor, that addressed similar deficiencies. The LSx engines are better in every respect than the old SBC.
The C4 featured different performance variants of the SBC, the same engine you just lamented the loss of above. The L98, LT1 and LT4 are all 350ci SBC's. The SBC saw numerous "tweaks" over the years, such as different fuel injection systems, as those evolved, and different ignition systems, such as going from HEI to Optispark, where the distributor was moved from the back, squeezed under the cowling at the firewall, to the timing cover, where it was driven off the cam gear.
Chrysler's MDS system has been extremely reliable. While there have been some lifter failures, that's a supplier problem with the lifters themselves and has nothing to do with the variable displacement system and has impacted non-MDS engines as well. GM has had a similar problem with their AFM engines, also lifter failures, likely the same supplier. However, GM also had a problem with their AFM engines consuming oil, a problem FCA hasn't had.
Honda's VTEC is their variable valve timing (not displacement) system. Their variable displacement system was called VCM and because it didn't alternate cylinders and some other poor choices, had a tendency to create sludge/varnish.
@Trav has a lot of experience dealing with this in the Honda V6's.
The main complaints about MDS are the "stumble" you might experience if you kick it out of MDS when it's trying to shift or accelerate at low RPM, the rumble, which in some platforms that don't have the active isolators, you can feel, and the exhaust note, which, if you have aftermarket exhaust, gets a bit funky when it's running as a 4-pot. I own two MDS equipped vehicle and other than the exhaust note, it is mostly imperceptible on the RAM because of the active isolation system which uses frame-mounted electronic dampening devices that cancel out the MDS "rumble". The SRT, I'm sitting much closer to the engine and it lacks that feature, so you can feel a bit of a rumble when it goes in and out of MDS, though you can't really hear it in the exhaust because that's factory.
I've owned 4x 6.4L MDS vehicles and 2x 5.7L MDS ones. We also have a small fleet of RAM 1500's at work. We've had absolutely zero issues with the system over roughly a combined fleet mileage of ~1.4 million miles (2.1 million Km) and only one case of lifter failure.